Add and use isInteger function where appropriate.

Replace some recent android API features with backwards compatible ones.

.gitignore

@@ -24,7 +24,9 @@ hs_err_pid*
 # Custom Stuff
 # Gradle
 .gradle/*
-build/*
+**/build/*
+**/out/**
+**/.DS_Store
 
 # IntelliJ
 .idea/*

core/build.gradle

@@ -1,4 +1,3 @@
 dependencies {
-    compile 'com.moandjiezana.toml:toml4j:0.7.1'
     testCompile 'junit:junit:4.12'
 }

core/src/main/java/org/nwapw/abacus/Abacus.java

@@ -1,135 +0,0 @@
-package org.nwapw.abacus;
-
-import org.nwapw.abacus.config.Configuration;
-import org.nwapw.abacus.number.NumberInterface;
-import org.nwapw.abacus.parsing.LexerTokenizer;
-import org.nwapw.abacus.parsing.ShuntingYardParser;
-import org.nwapw.abacus.parsing.TreeBuilder;
-import org.nwapw.abacus.plugin.NumberImplementation;
-import org.nwapw.abacus.plugin.PluginManager;
-import org.nwapw.abacus.plugin.StandardPlugin;
-import org.nwapw.abacus.tree.NumberReducer;
-import org.nwapw.abacus.tree.TreeNode;
-
-/**
- * The main calculator class. This is responsible
- * for piecing together all of the components, allowing
- * their interaction with each other.
- */
-public class Abacus {
-
-    /**
-     * The default number implementation to be used if no other one is available / selected.
-     */
-    public static final NumberImplementation DEFAULT_IMPLEMENTATION = StandardPlugin.IMPLEMENTATION_NAIVE;
-
-    /**
-     * The plugin manager responsible for
-     * loading and unloading plugins,
-     * and getting functions from them.
-     */
-    private PluginManager pluginManager;
-    /**
-     * The reducer used to evaluate the tree.
-     */
-    private NumberReducer numberReducer;
-    /**
-     * The configuration loaded from a file.
-     */
-    private Configuration configuration;
-    /**
-     * The tree builder used to construct a tree
-     * from a string.
-     */
-    private TreeBuilder treeBuilder;
-
-    /**
-     * Creates a new instance of the Abacus calculator.
-     *
-     * @param configuration the configuration object for this Abacus instance.
-     */
-    public Abacus(Configuration configuration) {
-        pluginManager = new PluginManager(this);
-        numberReducer = new NumberReducer(this);
-        this.configuration = new Configuration(configuration);
-        LexerTokenizer lexerTokenizer = new LexerTokenizer();
-        ShuntingYardParser shuntingYardParser = new ShuntingYardParser();
-        treeBuilder = new TreeBuilder<>(lexerTokenizer, shuntingYardParser);
-
-        pluginManager.addListener(shuntingYardParser);
-        pluginManager.addListener(lexerTokenizer);
-    }
-
-    /**
-     * Gets the current tree builder.
-     *
-     * @return the main tree builder in this abacus instance.
-     */
-    public TreeBuilder getTreeBuilder() {
-        return treeBuilder;
-    }
-
-    /**
-     * Gets the current plugin manager,
-     *
-     * @return the plugin manager in this abacus instance.
-     */
-    public PluginManager getPluginManager() {
-        return pluginManager;
-    }
-
-    /**
-     * Get the reducer that is responsible for transforming
-     * an expression into a number.
-     *
-     * @return the number reducer in this abacus instance.
-     */
-    public NumberReducer getNumberReducer() {
-        return numberReducer;
-    }
-
-    /**
-     * Gets the configuration object associated with this instance.
-     *
-     * @return the configuration object.
-     */
-    public Configuration getConfiguration() {
-        return configuration;
-    }
-
-    /**
-     * Parses a string into a tree structure using the main
-     * tree builder.
-     *
-     * @param input the input string to parse
-     * @return the resulting tree, null if the tree builder or the produced tree are null.
-     */
-    public TreeNode parseString(String input) {
-        return treeBuilder.fromString(input);
-    }
-
-    /**
-     * Evaluates the given tree using the main
-     * number reducer.
-     *
-     * @param tree the tree to reduce, must not be null.
-     * @return the resulting number, or null of the reduction failed.
-     */
-    public NumberInterface evaluateTree(TreeNode tree) {
-        return tree.reduce(numberReducer);
-    }
-
-    /**
-     * Creates a number from a string.
-     *
-     * @param numberString the string to create the number from.
-     * @return the resulting number.
-     */
-    public NumberInterface numberFromString(String numberString) {
-        NumberImplementation toInstantiate =
-                pluginManager.numberImplementationFor(configuration.getNumberImplementation());
-        if (toInstantiate == null) toInstantiate = DEFAULT_IMPLEMENTATION;
-
-        return toInstantiate.instanceForString(numberString);
-    }
-}

core/src/main/java/org/nwapw/abacus/config/Configuration.java

@@ -1,159 +0,0 @@
-package org.nwapw.abacus.config;
-
-import com.moandjiezana.toml.Toml;
-import com.moandjiezana.toml.TomlWriter;
-
-import java.io.File;
-import java.io.IOException;
-import java.util.Arrays;
-import java.util.HashSet;
-import java.util.Set;
-
-/**
- * The configuration object that stores
- * options that the user can change.
- */
-public class Configuration {
-
-    /**
-     * The defaults TOML string.
-     */
-    private static final String DEFAULT_CONFIG =
-            "numberImplementation = \"naive\"\n" +
-                    "disabledPlugins = []";
-    /**
-     * The defaults TOML object, parsed from the string.
-     */
-    private static final Toml DEFAULT_TOML = new Toml().read(DEFAULT_CONFIG);
-    /**
-     * The TOML writer used to write this configuration to a file.
-     */
-    private static final TomlWriter TOML_WRITER = new TomlWriter();
-
-    /**
-     * The computation delay for which the thread can run without interruption.
-     */
-    private double computationDelay = 0;
-    /**
-     * The implementation of the number that should be used.
-     */
-    private String numberImplementation = "<default>";
-    /**
-     * The list of disabled plugins in this Configuration.
-     */
-    private Set<String> disabledPlugins = new HashSet<>();
-
-    /**
-     * Creates a new configuration form the given configuration.
-     *
-     * @param copyFrom the configuration to copy.
-     */
-    public Configuration(Configuration copyFrom) {
-        copyFrom(copyFrom);
-    }
-
-    /**
-     * Creates a new configuration with the given values.
-     *
-     * @param computationDelay     the delay before the computation gets killed.
-     * @param numberImplementation the number implementation, like "naive" or "precise"
-     * @param disabledPlugins      the list of disabled plugins.
-     */
-    public Configuration(double computationDelay, String numberImplementation, String[] disabledPlugins) {
-        this.computationDelay = computationDelay;
-        this.numberImplementation = numberImplementation;
-        this.disabledPlugins.addAll(Arrays.asList(disabledPlugins));
-    }
-
-    /**
-     * Loads a configuration from a given file, keeping non-specified fields default.
-     *
-     * @param fromFile the file to load from.
-     */
-    public Configuration(File fromFile) {
-        if (!fromFile.exists()) return;
-        copyFrom(new Toml(DEFAULT_TOML).read(fromFile).to(Configuration.class));
-    }
-
-    /**
-     * Copies the values from the given configuration into this one.
-     *
-     * @param otherConfiguration the configuration to copy from.
-     */
-    public void copyFrom(Configuration otherConfiguration) {
-        this.computationDelay = otherConfiguration.computationDelay;
-        this.numberImplementation = otherConfiguration.numberImplementation;
-        this.disabledPlugins.addAll(otherConfiguration.disabledPlugins);
-    }
-
-    /**
-     * Saves this configuration to the given file, creating
-     * any directories that do not exist.
-     *
-     * @param file the file to save to.
-     */
-    public void saveTo(File file) {
-        if (file.getParentFile() != null) file.getParentFile().mkdirs();
-        try {
-            TOML_WRITER.write(this, file);
-        } catch (IOException e) {
-            e.printStackTrace();
-        }
-    }
-
-    /**
-     * Gets the value of this configuration as a string.
-     *
-     * @return the string that represents this configuration.
-     */
-    public String asTomlString() {
-        return TOML_WRITER.write(this);
-    }
-
-    /**
-     * Gets the number implementation from this configuration.
-     *
-     * @return the number implementation.
-     */
-    public String getNumberImplementation() {
-        return numberImplementation;
-    }
-
-    /**
-     * Sets the number implementation for the configuration
-     *
-     * @param numberImplementation the number implementation.
-     */
-    public void setNumberImplementation(String numberImplementation) {
-        this.numberImplementation = numberImplementation;
-    }
-
-    /**
-     * Gets the list of disabled plugins.
-     *
-     * @return the list of disabled plugins.
-     */
-    public Set<String> getDisabledPlugins() {
-        return disabledPlugins;
-    }
-
-
-    /**
-     * Gets the computation delay specified in the configuration.
-     *
-     * @return the computaton delay.
-     */
-    public double getComputationDelay() {
-        return computationDelay;
-    }
-
-    /**
-     * Sets the computation delay.
-     *
-     * @param computationDelay the new computation delay.
-     */
-    public void setComputationDelay(double computationDelay) {
-        this.computationDelay = computationDelay;
-    }
-
-}

core/src/main/java/org/nwapw/abacus/exception/AbacusException.java

@@ -0,0 +1,9 @@
+package org.nwapw.abacus.exception;
+
+public class AbacusException extends RuntimeException {
+
+    public AbacusException(String baseMessage, String description){
+        super(baseMessage + ((description.equals("")) ? "." : (": " + description)));
+    }
+
+}

core/src/main/java/org/nwapw/abacus/exception/ComputationInterruptedException.java

@@ -1,16 +1,16 @@
-package org.nwapw.abacus.number;
+package org.nwapw.abacus.exception;
 
 /**
  * Exception thrown when the computation is interrupted by
  * the user.
  */
-public class ComputationInterruptedException extends RuntimeException {
+public class ComputationInterruptedException extends AbacusException {
 
     /**
      * Creates a new exception of this type.
      */
     public ComputationInterruptedException() {
-        super("Computation interrupted by user.");
+        super("Computation interrupted", "");
     }
 
 }

core/src/main/java/org/nwapw/abacus/exception/ContextException.java

@@ -0,0 +1,24 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * Exception thrown by the Context in cases where lookup fails
+ * where it should not.
+ */
+public class ContextException extends AbacusException {
+
+    /**
+     * Creates a new ContextException without an extra message.
+     */
+    public ContextException() {
+        this("");
+    }
+
+    /**
+     * Creates a ContextException with the given message.
+     * @param message the message to use.
+     */
+    public ContextException(String message){
+        super("Context exception", message);
+    }
+
+}

core/src/main/java/org/nwapw/abacus/exception/DomainException.java

@@ -0,0 +1,24 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * Exception thrown if the function parameters do not match
+ * requirements.
+ */
+public class DomainException extends AbacusException {
+
+    /**
+     * Creates a new DomainException.
+     * @param reason the reason for which the exception is thrown.
+     */
+    public DomainException(String reason) {
+        super("Domain error", reason);
+    }
+
+    /**
+     * Creates a new DomainException with a default message.
+     */
+    public DomainException(){
+        this("");
+    }
+
+}

core/src/main/java/org/nwapw/abacus/exception/NumberReducerException.java

@@ -0,0 +1,25 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * Exception thrown by the NumberReducer if something goes wrong when
+ * transforming a parse tree into a single value.
+ */
+public class NumberReducerException extends AbacusException {
+
+    /**
+     * Creates a new NumberReducerException with
+     * no additional message.
+     */
+    public NumberReducerException() {
+        this("");
+    }
+
+    /**
+     * Creates a new NumberReducerException with the given message.
+     * @param message the message.
+     */
+    public NumberReducerException(String message) {
+        super("Error evaluating expression", message);
+    }
+
+}

core/src/main/java/org/nwapw/abacus/exception/ParseException.java

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * Exception thrown by parsers.
+ */
+public class ParseException extends AbacusException {
+
+    /**
+     * Creates a new ParseException with no additional message.
+     */
+    public ParseException(){
+        this("");
+    }
+
+    /**
+     * Creates a new ParseException with the given additional message.
+     * @param message the message.
+     */
+    public ParseException(String message){
+        super("Failed to parse string", message);
+    }
+
+}

core/src/main/java/org/nwapw/abacus/exception/PromotionException.java

@@ -0,0 +1,24 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * Exception thrown when a promotion fails.
+ */
+public class PromotionException extends AbacusException {
+
+    /**
+     * Creates a new PromotionException with the default message
+     * and no additional information.
+     */
+    public PromotionException() {
+        this("");
+    }
+
+    /**
+     * Creates a new PromotionException with the given additional message.
+     * @param message the additional message to include with the error.
+     */
+    public PromotionException(String message) {
+        super("Failed to promote number instances", message);
+    }
+
+}

core/src/main/java/org/nwapw/abacus/exception/ReductionException.java

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * An exception thrown from TreeReducers.
+ */
+public class ReductionException extends AbacusException {
+
+    /**
+     * Creates a new EvaluationException with the default string.
+     */
+    public ReductionException() {
+        this("");
+    }
+
+    /**
+     * Creates a new EvaluationError with the given message string.
+     * @param message the message string.
+     */
+    public ReductionException(String message) {
+        super("Evaluation error", message);
+    }
+
+}

core/src/main/java/org/nwapw/abacus/exception/TokenizeException.java

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * Exception thrown by Lexers when they are unable to tokenize the input string.
+ */
+public class TokenizeException extends AbacusException {
+
+    /**
+     * Create a new tokenize exception with no additional data.
+     */
+    public TokenizeException() {
+        this("");
+    }
+
+    /**
+     * Create a new tokenize exception with the given message.
+     * @param message the message to use.
+     */
+    public TokenizeException(String message){
+        super("Failed to tokenize string", message);
+    }
+
+}

core/src/main/java/org/nwapw/abacus/lexing/Lexer.java

@@ -1,9 +1,8 @@
 package org.nwapw.abacus.lexing;
 
-import org.nwapw.abacus.lexing.pattern.EndNode;
+import org.nwapw.abacus.lexing.pattern.nodes.EndNode;
-import org.nwapw.abacus.lexing.pattern.Match;
 import org.nwapw.abacus.lexing.pattern.Pattern;
-import org.nwapw.abacus.lexing.pattern.PatternNode;
+import org.nwapw.abacus.lexing.pattern.nodes.PatternNode;
 
 import java.util.*;
 
@@ -80,10 +79,10 @@ public class Lexer<T> {
 
             index++;
         }
-        matches.sort((a, b) -> compare.compare(a.getType(), b.getType()));
         if (compare != null) {
-            matches.sort(Comparator.comparingInt(a -> a.getContent().length()));
+            Collections.sort(matches, (a, b) -> compare.compare(a.getType(), b.getType()));
         }
+        Collections.sort(matches, (o1, o2) -> o1.getContent().length() - o2.getContent().length());
         return matches.isEmpty() ? null : matches.get(matches.size() - 1);
     }
 
@@ -137,7 +136,10 @@ public class Lexer<T> {
 
         @Override
         public int hashCode() {
-            return Objects.hash(name, id);
+            return Arrays.hashCode(new Object[] {
+                    this.name,
+                    this.id
+            });
         }
 
         @Override

core/src/main/java/org/nwapw/abacus/lexing/Match.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.lexing.pattern;
+package org.nwapw.abacus.lexing;
 
 /**
  * A match that has been generated by the lexer.

core/src/main/java/org/nwapw/abacus/lexing/pattern/Pattern.java

@@ -1,10 +1,11 @@
 package org.nwapw.abacus.lexing.pattern;
 
+import org.nwapw.abacus.lexing.pattern.nodes.*;
+
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Stack;
-import java.util.function.Function;
 
 /**
  * A pattern that can be compiled from a string and used in lexing.
@@ -34,8 +35,8 @@ public class Pattern<T> {
      * A map of regex operator to functions that modify a PatternChain
      * with the appropriate operation.
      */
-    private Map<Character, Function<PatternChain<T>, PatternChain<T>>> operations =
+    private Map<Character, Transformation<T>> operations =
-            new HashMap<Character, Function<PatternChain<T>, PatternChain<T>>>() {{
+            new HashMap<Character, Transformation<T>>() {{
                 put('+', Pattern.this::transformPlus);
                 put('*', Pattern.this::transformStar);
                 put('?', Pattern.this::transformQuestion);
@@ -88,7 +89,7 @@ public class Pattern<T> {
      * @return the modified chain.
      */
     private PatternChain<T> transformPlus(PatternChain<T> chain) {
-        chain.tail.outputStates.add(chain.head);
+        chain.tail.getOutputStates().add(chain.head);
         return chain;
     }
 
@@ -102,10 +103,10 @@ public class Pattern<T> {
     private PatternChain<T> transformStar(PatternChain<T> chain) {
         LinkNode<T> newTail = new LinkNode<>();
         LinkNode<T> newHead = new LinkNode<>();
-        newHead.outputStates.add(chain.head);
+        newHead.getOutputStates().add(chain.head);
-        newHead.outputStates.add(newTail);
+        newHead.getOutputStates().add(newTail);
-        chain.tail.outputStates.add(newTail);
+        chain.tail.getOutputStates().add(newTail);
-        newTail.outputStates.add(newHead);
+        newTail.getOutputStates().add(newHead);
         chain.head = newHead;
         chain.tail = newTail;
         return chain;
@@ -121,9 +122,9 @@ public class Pattern<T> {
     private PatternChain<T> transformQuestion(PatternChain<T> chain) {
         LinkNode<T> newTail = new LinkNode<>();
         LinkNode<T> newHead = new LinkNode<>();
-        newHead.outputStates.add(chain.head);
+        newHead.getOutputStates().add(chain.head);
-        newHead.outputStates.add(newTail);
+        newHead.getOutputStates().add(newTail);
-        chain.tail.outputStates.add(newTail);
+        chain.tail.getOutputStates().add(newTail);
         chain.head = newHead;
         chain.tail = newTail;
         return chain;
@@ -140,8 +141,8 @@ public class Pattern<T> {
         LinkNode<T> tail = new LinkNode<>();
         PatternChain<T> newChain = new PatternChain<>(head, tail);
         for (PatternChain<T> chain : collection) {
-            head.outputStates.add(chain.head);
+            head.getOutputStates().add(chain.head);
-            chain.tail.outputStates.add(tail);
+            chain.tail.getOutputStates().add(tail);
         }
         return newChain;
     }
@@ -205,7 +206,7 @@ public class Pattern<T> {
             if (operations.containsKey(currentChar)) {
                 if (currentChain == null) return null;
 
-                currentChain = operations.get(currentChar).apply(currentChain);
+                currentChain = operations.get(currentChar).transform(currentChain);
                 fullChain.append(currentChain);
                 currentChain = null;
                 index++;

core/src/main/java/org/nwapw/abacus/lexing/pattern/PatternChain.java

@@ -1,5 +1,7 @@
 package org.nwapw.abacus.lexing.pattern;
 
+import org.nwapw.abacus.lexing.pattern.nodes.PatternNode;
+
 /**
  * A chain of nodes that can be treated as a single unit.
  * Used during pattern compilation.
@@ -56,7 +58,7 @@ public class PatternChain<T> {
             this.head = other.head;
             this.tail = other.tail;
         } else {
-            tail.outputStates.add(other.head);
+            tail.getOutputStates().add(other.head);
             tail = other.tail;
         }
     }
@@ -72,7 +74,7 @@ public class PatternChain<T> {
         if (tail == null) {
             head = tail = node;
         } else {
-            tail.outputStates.add(node);
+            tail.getOutputStates().add(node);
             tail = node;
         }
     }

core/src/main/java/org/nwapw/abacus/lexing/pattern/Transformation.java

@@ -0,0 +1,16 @@
+package org.nwapw.abacus.lexing.pattern;
+
+/**
+ * An interface that transforms a pattern chain into a different pattern chain.
+ * @param <T> the type used to identify the nodes in the pattern chain.
+ */
+public interface Transformation<T> {
+
+    /**
+     * Performs the actual transformation.
+     * @param from the original chain.
+     * @return the resulting chain.
+     */
+    PatternChain<T> transform(PatternChain<T> from);
+
+}

core/src/main/java/org/nwapw/abacus/lexing/pattern/nodes/AnyNode.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.lexing.pattern;
+package org.nwapw.abacus.lexing.pattern.nodes;
 
 /**
  * A pattern node that matches any character.

core/src/main/java/org/nwapw/abacus/lexing/pattern/nodes/EndNode.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.lexing.pattern;
+package org.nwapw.abacus.lexing.pattern.nodes;
 
 /**
  * A node that represents a successful match.

core/src/main/java/org/nwapw/abacus/lexing/pattern/nodes/LinkNode.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.lexing.pattern;
+package org.nwapw.abacus.lexing.pattern.nodes;
 
 import java.util.Collection;
 

core/src/main/java/org/nwapw/abacus/lexing/pattern/nodes/PatternNode.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.lexing.pattern;
+package org.nwapw.abacus.lexing.pattern.nodes;
 
 import java.util.Collection;
 import java.util.HashSet;
@@ -65,4 +65,11 @@ public class PatternNode<T> {
         outputStates.forEach(e -> e.addInto(into));
     }
 
+    /**
+     * Gets the output states of this node.
+     * @return the output states.
+     */
+    public Set<PatternNode<T>> getOutputStates() {
+        return outputStates;
+    }
 }

core/src/main/java/org/nwapw/abacus/lexing/pattern/nodes/RangeNode.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.lexing.pattern;
+package org.nwapw.abacus.lexing.pattern.nodes;
 
 /**
  * A node that matches a range of characters.

core/src/main/java/org/nwapw/abacus/lexing/pattern/nodes/ValueNode.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.lexing.pattern;
+package org.nwapw.abacus.lexing.pattern.nodes;
 
 /**
  * A node that matches a single value.

core/src/main/java/org/nwapw/abacus/number/standard/NaiveNumber.java

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.number;
+package org.nwapw.abacus.number.standard;
+
+import org.nwapw.abacus.number.NumberInterface;
 
 /**
  * An implementation of NumberInterface using a double.
@@ -114,15 +116,6 @@ public class NaiveNumber extends NumberInterface {
         return (int) value;
     }
 
-    @Override
-    public NumberInterface promoteToInternal(Class<? extends NumberInterface> toClass) {
-        if (toClass == this.getClass()) return this;
-        else if (toClass == PreciseNumber.class) {
-            return new PreciseNumber(Double.toString(value));
-        }
-        return null;
-    }
-
     public String toString() {
         double shiftBy = Math.pow(10, 10);
         return Double.toString(Math.round(value * shiftBy) / shiftBy);

core/src/main/java/org/nwapw/abacus/number/standard/PreciseNumber.java

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.number;
+package org.nwapw.abacus.number.standard;
+
+import org.nwapw.abacus.number.NumberInterface;
 
 import java.math.BigDecimal;
 import java.math.MathContext;
@@ -152,14 +154,6 @@ public class PreciseNumber extends NumberInterface {
         return new PreciseNumber(value.negate());
     }
 
-    @Override
-    public NumberInterface promoteToInternal(Class<? extends NumberInterface> toClass) {
-        if (toClass == this.getClass()) {
-            return this;
-        }
-        return null;
-    }
-
     @Override
     public String toString() {
         return value.round(outputContext).toString();

core/src/main/java/org/nwapw/abacus/parsing/Tokenizer.java

@@ -1,20 +0,0 @@
-package org.nwapw.abacus.parsing;
-
-import java.util.List;
-
-/**
- * Interface that provides the ability to convert a string into a list of tokens.
- *
- * @param <T> the type of the tokens produced.
- */
-public interface Tokenizer<T> {
-
-    /**
-     * Converts a string into tokens.
-     *
-     * @param string the string to convert.
-     * @return the list of tokens, or null on error.
-     */
-    public List<T> tokenizeString(String string);
-
-}

core/src/main/java/org/nwapw/abacus/parsing/TreeBuilder.java

@@ -1,50 +0,0 @@
-package org.nwapw.abacus.parsing;
-
-import org.nwapw.abacus.tree.TreeNode;
-
-import java.util.List;
-
-/**
- * TreeBuilder class used to piece together a Tokenizer and
- * Parser of the same kind. This is used to essentially avoid
- * working with any parameters at all, and the generics
- * in this class are used only to ensure the tokenizer and parser
- * are of the same type.
- *
- * @param <T> the type of tokens created by the tokenizer and used by the parser.
- */
-public class TreeBuilder<T> {
-
-    /**
-     * The tokenizer used to convert a string into tokens.
-     */
-    private Tokenizer<T> tokenizer;
-    /**
-     * The parser used to parse a list of tokens into a tree.
-     */
-    private Parser<T> parser;
-
-    /**
-     * Create a new Tree Builder with the given tokenizer and parser
-     *
-     * @param tokenizer the tokenizer to turn strings into tokens
-     * @param parser    the parser to turn tokens into a tree
-     */
-    public TreeBuilder(Tokenizer<T> tokenizer, Parser<T> parser) {
-        this.tokenizer = tokenizer;
-        this.parser = parser;
-    }
-
-    /**
-     * Parse the given string into a tree.
-     *
-     * @param input the string to parse into a tree.
-     * @return the resulting tree.
-     */
-    public TreeNode fromString(String input) {
-        List<T> tokens = tokenizer.tokenizeString(input);
-        if (tokens == null) return null;
-        return parser.constructTree(tokens);
-    }
-
-}

core/src/main/java/org/nwapw/abacus/parsing/standard/LexerTokenizer.java

@@ -1,11 +1,12 @@
-package org.nwapw.abacus.parsing;
+package org.nwapw.abacus.parsing.standard;
 
+import org.nwapw.abacus.exception.TokenizeException;
 import org.nwapw.abacus.lexing.Lexer;
-import org.nwapw.abacus.lexing.pattern.Match;
+import org.nwapw.abacus.lexing.Match;
 import org.nwapw.abacus.lexing.pattern.Pattern;
+import org.nwapw.abacus.parsing.Tokenizer;
 import org.nwapw.abacus.plugin.PluginListener;
 import org.nwapw.abacus.plugin.PluginManager;
-import org.nwapw.abacus.tree.TokenType;
 
 import java.util.Comparator;
 import java.util.List;
@@ -19,7 +20,7 @@ public class LexerTokenizer implements Tokenizer<Match<TokenType>>, PluginListen
     /**
      * Comparator used to sort the tokens produced by the lexer.
      */
-    protected static final Comparator<TokenType> TOKEN_SORTER = Comparator.comparingInt(e -> e.priority);
+    protected static final Comparator<TokenType> TOKEN_SORTER = (o1, o2) -> o1.priority - o2.priority;
 
     /**
      * The lexer instance used to turn strings into matches.
@@ -42,7 +43,9 @@ public class LexerTokenizer implements Tokenizer<Match<TokenType>>, PluginListen
 
     @Override
     public List<Match<TokenType>> tokenizeString(String string) {
-        return lexer.lexAll(string, 0, TOKEN_SORTER);
+        List<Match<TokenType>> tokens = lexer.lexAll(string, 0, TOKEN_SORTER);
+        if(tokens == null) throw new TokenizeException();
+        return tokens;
     }
 
     @Override
@@ -50,13 +53,13 @@ public class LexerTokenizer implements Tokenizer<Match<TokenType>>, PluginListen
         for (String operator : manager.getAllOperators()) {
             lexer.register(Pattern.sanitize(operator), TokenType.OP);
         }
-        for (String operator : manager.getAllTreeValueOperators()){
+        for (String operator : manager.getAllTreeValueOperators()) {
             lexer.register(Pattern.sanitize(operator), TokenType.TREE_VALUE_OP);
         }
         for (String function : manager.getAllFunctions()) {
             lexer.register(Pattern.sanitize(function), TokenType.FUNCTION);
         }
-        for (String function : manager.getAllTreeValueFunctions()){
+        for (String function : manager.getAllTreeValueFunctions()) {
             lexer.register(Pattern.sanitize(function), TokenType.TREE_VALUE_FUNCTION);
         }
     }
@@ -66,13 +69,13 @@ public class LexerTokenizer implements Tokenizer<Match<TokenType>>, PluginListen
         for (String operator : manager.getAllOperators()) {
             lexer.unregister(Pattern.sanitize(operator), TokenType.OP);
         }
-        for (String operator : manager.getAllTreeValueOperators()){
+        for (String operator : manager.getAllTreeValueOperators()) {
             lexer.unregister(Pattern.sanitize(operator), TokenType.TREE_VALUE_OP);
         }
         for (String function : manager.getAllFunctions()) {
             lexer.unregister(Pattern.sanitize(function), TokenType.FUNCTION);
         }
-        for (String function : manager.getAllTreeValueFunctions()){
+        for (String function : manager.getAllTreeValueFunctions()) {
             lexer.unregister(Pattern.sanitize(function), TokenType.TREE_VALUE_FUNCTION);
         }
     }

core/src/main/java/org/nwapw/abacus/parsing/standard/ShuntingYardParser.java

@@ -1,12 +1,14 @@
-package org.nwapw.abacus.parsing;
+package org.nwapw.abacus.parsing.standard;
 
+import org.nwapw.abacus.exception.ParseException;
 import org.nwapw.abacus.function.Operator;
 import org.nwapw.abacus.function.OperatorAssociativity;
 import org.nwapw.abacus.function.OperatorType;
-import org.nwapw.abacus.lexing.pattern.Match;
+import org.nwapw.abacus.lexing.Match;
+import org.nwapw.abacus.parsing.Parser;
 import org.nwapw.abacus.plugin.PluginListener;
 import org.nwapw.abacus.plugin.PluginManager;
-import org.nwapw.abacus.tree.*;
+import org.nwapw.abacus.tree.nodes.*;
 
 import java.util.*;
 
@@ -99,7 +101,7 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
                 while (!tokenStack.empty() && tokenStack.peek().getType() != TokenType.OPEN_PARENTH) {
                     output.add(tokenStack.pop());
                 }
-                if (tokenStack.empty()) return null;
+                if (tokenStack.empty()) throw new ParseException("mismatched parentheses");
                 if (matchType == TokenType.CLOSE_PARENTH) {
                     tokenStack.pop();
                 }
@@ -111,7 +113,7 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
             if (!(newMatchType == TokenType.OP ||
                     newMatchType == TokenType.TREE_VALUE_OP ||
                     newMatchType == TokenType.FUNCTION ||
-                    newMatchType == TokenType.TREE_VALUE_FUNCTION)) return null;
+                    newMatchType == TokenType.TREE_VALUE_FUNCTION)) throw new ParseException("mismatched parentheses");
             output.add(tokenStack.pop());
         }
         return output;
@@ -123,8 +125,8 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
      * @param matches the list of tokens from the source string.
      * @return the construct tree expression.
      */
-    public TreeNode constructRecursive(List<Match<TokenType>> matches) {
+    public TreeNode constructRecursive(List<? extends Match<TokenType>> matches) {
-        if (matches.size() == 0) return null;
+        if (matches.size() == 0) throw new ParseException("no tokens left in input");
         Match<TokenType> match = matches.remove(0);
         TokenType matchType = match.getType();
         if (matchType == TokenType.OP || matchType == TokenType.TREE_VALUE_OP) {
@@ -133,16 +135,14 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
             if (type == OperatorType.BINARY_INFIX) {
                 TreeNode right = constructRecursive(matches);
                 TreeNode left = constructRecursive(matches);
-                if (left == null || right == null) return null;
+                if (matchType == TokenType.OP) {
-                if(matchType == TokenType.OP) {
                     return new NumberBinaryNode(operator, left, right);
                 } else {
                     return new TreeValueBinaryNode(operator, left, right);
                 }
             } else {
                 TreeNode applyTo = constructRecursive(matches);
-                if (applyTo == null) return null;
+                if (matchType == TokenType.OP) {
-                if(matchType == TokenType.OP){
                     return new NumberUnaryNode(operator, applyTo);
                 } else {
                     return new TreeValueUnaryNode(operator, applyTo);
@@ -154,31 +154,32 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
             return new VariableNode(match.getContent());
         } else if (matchType == TokenType.FUNCTION || matchType == TokenType.TREE_VALUE_FUNCTION) {
             String functionName = match.getContent();
-            CallNode node;
+            List<TreeNode> children = new ArrayList<>();
-            if(matchType == TokenType.FUNCTION){
-                node = new FunctionNode(functionName);
-            } else {
-                node = new TreeValueFunctionNode(functionName);
-            }
             while (!matches.isEmpty() && matches.get(0).getType() != TokenType.INTERNAL_FUNCTION_END) {
                 TreeNode argument = constructRecursive(matches);
-                if (argument == null) return null;
+                children.add(0, argument);
-                node.getChildren().add(0, argument);
             }
-            if (matches.isEmpty()) return null;
+            if (matches.isEmpty()) throw new ParseException("incorrectly formatted function call");
             matches.remove(0);
+            CallNode node;
+            if (matchType == TokenType.FUNCTION) {
+                node = new NumberFunctionNode(functionName, children);
+            } else {
+                node = new TreeValueFunctionNode(functionName, children);
+            }
             return node;
         }
-        return null;
+        throw new ParseException("unrecognized token");
     }
 
     @Override
-    public TreeNode constructTree(List<Match<TokenType>> tokens) {
+    public TreeNode constructTree(List<? extends Match<TokenType>> tokens) {
+        if (tokens.isEmpty()) throw new ParseException("no input tokens");
         tokens = intoPostfix(new ArrayList<>(tokens));
-        if (tokens == null) return null;
         Collections.reverse(tokens);
         TreeNode constructedTree = constructRecursive(tokens);
-        return tokens.size() == 0 ? constructedTree : null;
+        if(tokens.size() == 0) return constructedTree;
+        throw new ParseException("could not parse all input");
     }
 
     @Override

core/src/main/java/org/nwapw/abacus/parsing/standard/TokenType.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.tree;
+package org.nwapw.abacus.parsing.standard;
 
 /**
  * Enum to represent the type of the token that has been matched

core/src/main/java/org/nwapw/abacus/plugin/NumberImplementation.java

@@ -1,10 +1,10 @@
 package org.nwapw.abacus.plugin;
 
 import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.number.promotion.PromotionFunction;
 
 import java.util.HashMap;
 import java.util.Map;
-import java.util.function.Function;
 
 /**
  * A class that holds data about a number implementation.
@@ -14,7 +14,7 @@ public abstract class NumberImplementation {
     /**
      * The list of paths through which this implementation can be promoted.
      */
-    private Map<Class<? extends NumberInterface>, Function<NumberInterface, NumberInterface>> promotionPaths;
+    private Map<String, PromotionFunction> promotionPaths;
     /**
      * The implementation class for this implementation.
      */
@@ -41,7 +41,7 @@ public abstract class NumberImplementation {
      *
      * @return the map of documentation paths.
      */
-    public final Map<Class<? extends NumberInterface>, Function<NumberInterface, NumberInterface>> getPromotionPaths() {
+    public final Map<String, PromotionFunction> getPromotionPaths() {
         return promotionPaths;
     }
 

core/src/main/java/org/nwapw/abacus/plugin/Plugin.java

@@ -1,6 +1,10 @@
 package org.nwapw.abacus.plugin;
 
 import org.nwapw.abacus.function.*;
+import org.nwapw.abacus.function.interfaces.NumberFunction;
+import org.nwapw.abacus.function.interfaces.NumberOperator;
+import org.nwapw.abacus.function.interfaces.TreeValueFunction;
+import org.nwapw.abacus.function.interfaces.TreeValueOperator;
 import org.nwapw.abacus.number.NumberInterface;
 
 /**

core/src/main/java/org/nwapw/abacus/plugin/PluginManager.java

@@ -2,6 +2,10 @@ package org.nwapw.abacus.plugin;
 
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.function.*;
+import org.nwapw.abacus.function.interfaces.NumberFunction;
+import org.nwapw.abacus.function.interfaces.NumberOperator;
+import org.nwapw.abacus.function.interfaces.TreeValueFunction;
+import org.nwapw.abacus.function.interfaces.TreeValueOperator;
 import org.nwapw.abacus.number.NumberInterface;
 
 import java.lang.reflect.InvocationTargetException;
@@ -49,10 +53,13 @@ public class PluginManager {
      */
     private Set<Documentation> registeredDocumentation;
     /**
-     * The list of number implementations that have been
+     * The list of number implementation names.
-     * found by their implementation class.
      */
-    private Map<Class<? extends NumberInterface>, NumberImplementation> cachedInterfaceImplementations;
+    private Map<Class<? extends NumberInterface>, String> interfaceImplementationNames;
+    /**
+     * The list of number implementations.
+     */
+    private Map<Class<? extends NumberInterface>, NumberImplementation> interfaceImplementations;
     /**
      * The pi values for each implementation class that have already been computer.
      */
@@ -82,7 +89,8 @@ public class PluginManager {
         registeredTreeValueOperators = new HashMap<>();
         registeredNumberImplementations = new HashMap<>();
         registeredDocumentation = new HashSet<>();
-        cachedInterfaceImplementations = new HashMap<>();
+        interfaceImplementations = new HashMap<>();
+        interfaceImplementationNames = new HashMap<>();
         cachedPi = new HashMap<>();
         listeners = new HashSet<>();
     }
@@ -135,6 +143,9 @@ public class PluginManager {
      */
     public void registerNumberImplementation(String name, NumberImplementation implementation) {
         registeredNumberImplementations.put(name, implementation);
+        interfaceImplementationNames.put(implementation.getImplementation(), name);
+        interfaceImplementations.put(implementation.getImplementation(), implementation);
+        cachedPi.put(implementation.getImplementation(), implementation.instanceForPi());
     }
 
     /**
@@ -212,10 +223,6 @@ public class PluginManager {
                 break;
             }
         }
-        if (toReturn == null) {
-            toReturn = new Documentation(name, "", "", "", type);
-            registerDocumentation(toReturn);
-        }
         return toReturn;
     }
 
@@ -226,17 +233,17 @@ public class PluginManager {
      * @return the implementation.
      */
     public NumberImplementation interfaceImplementationFor(Class<? extends NumberInterface> name) {
-        if (cachedInterfaceImplementations.containsKey(name)) return cachedInterfaceImplementations.get(name);
+        return interfaceImplementations.get(name);
-        NumberImplementation toReturn = null;
+    }
-        for (String key : registeredNumberImplementations.keySet()) {
+
-            NumberImplementation implementation = registeredNumberImplementations.get(key);
+    /**
-            if (implementation.getImplementation() == name) {
+     * Gets the number implementation name for the given implementation class.
-                toReturn = implementation;
+     *
-                break;
+     * @param name the class for which to find the implementation name.
-            }
+     * @return the implementation name.
-        }
+     */
-        cachedInterfaceImplementations.put(name, toReturn);
+    public String interfaceImplementationNameFor(Class<? extends NumberInterface> name) {
-        return toReturn;
+        return interfaceImplementationNames.get(name);
     }
 
     /**
@@ -246,14 +253,7 @@ public class PluginManager {
      * @return pi
      */
     public NumberInterface piFor(Class<? extends NumberInterface> forClass) {
-        if (cachedPi.containsKey(forClass)) return cachedPi.get(forClass);
+        return cachedPi.get(forClass);
-        NumberImplementation implementation = interfaceImplementationFor(forClass);
-        NumberInterface generatedPi = null;
-        if (implementation != null) {
-            generatedPi = implementation.instanceForPi();
-        }
-        cachedPi.put(forClass, generatedPi);
-        return generatedPi;
     }
 
     /**
@@ -329,7 +329,8 @@ public class PluginManager {
         registeredTreeValueOperators.clear();
         registeredNumberImplementations.clear();
         registeredDocumentation.clear();
-        cachedInterfaceImplementations.clear();
+        interfaceImplementationNames.clear();
+        interfaceImplementations.clear();
         cachedPi.clear();
         listeners.forEach(e -> e.onUnload(this));
     }
@@ -414,4 +415,5 @@ public class PluginManager {
     public Set<Class<?>> getLoadedPluginClasses() {
         return loadedPluginClasses;
     }
+    
 }

core/src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java

@@ -1,829 +0,0 @@
-package org.nwapw.abacus.plugin;
-
-import org.nwapw.abacus.function.*;
-import org.nwapw.abacus.number.NaiveNumber;
-import org.nwapw.abacus.number.NumberInterface;
-import org.nwapw.abacus.number.PreciseNumber;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.function.BiFunction;
-
-/**
- * The plugin providing standard functions such as addition and subtraction to
- * the calculator.
- */
-public class StandardPlugin extends Plugin {
-
-    /**
-     * The addition operator, +
-     */
-    public static final NumberOperator OP_ADD = new NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 2;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return params[0].add(params[1]);
-        }
-    };
-    /**
-     * The subtraction operator, -
-     */
-    public static final NumberOperator OP_SUBTRACT = new NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 2;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return params[0].subtract(params[1]);
-
-        }
-    };
-    /**
-     * The negation operator, -
-     */
-    public static final NumberOperator OP_NEGATE = new NumberOperator(OperatorAssociativity.LEFT, OperatorType.UNARY_PREFIX, 0) {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return params[0].negate();
-        }
-    };
-    /**
-     * The multiplication operator, *
-     */
-    public static final NumberOperator OP_MULTIPLY = new NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1) {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 2;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return params[0].multiply(params[1]);
-        }
-    };
-    /**
-     * The implementation for double-based naive numbers.
-     */
-    public static final NumberImplementation IMPLEMENTATION_NAIVE = new NumberImplementation(NaiveNumber.class, 0) {
-        @Override
-        public NumberInterface instanceForString(String string) {
-            return new NaiveNumber(string);
-        }
-
-        @Override
-        public NumberInterface instanceForPi() {
-            return new NaiveNumber(Math.PI);
-        }
-    };
-    /**
-     * The square root function.
-     */
-    public static final NumberFunction FUNCTION_SQRT = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return OP_CARET.apply(params[0], ((new NaiveNumber(0.5)).promoteTo(params[0].getClass())));
-        }
-    };
-    /**
-     * The implementation for the infinite-precision BigDecimal.
-     */
-    public static final NumberImplementation IMPLEMENTATION_PRECISE = new NumberImplementation(PreciseNumber.class, 0) {
-        @Override
-        public NumberInterface instanceForString(String string) {
-            return new PreciseNumber(string);
-        }
-
-        @Override
-        public NumberInterface instanceForPi() {
-            NumberInterface C = FUNCTION_SQRT.apply(new PreciseNumber("10005")).multiply(new PreciseNumber("426880"));
-            NumberInterface M = PreciseNumber.ONE;
-            NumberInterface L = new PreciseNumber("13591409");
-            NumberInterface X = M;
-            NumberInterface sum = L;
-            int termsNeeded = C.getMaxPrecision() / 13 + 1;
-
-            NumberInterface lSummand = new PreciseNumber("545140134");
-            NumberInterface xMultiplier = new PreciseNumber("262537412")
-                    .multiply(new PreciseNumber("1000000000"))
-                    .add(new PreciseNumber("640768000"))
-                    .negate();
-            for (int i = 0; i < termsNeeded; i++) {
-                M = M
-                        .multiply(new PreciseNumber((12 * i + 2) + ""))
-                        .multiply(new PreciseNumber((12 * i + 6) + ""))
-                        .multiply(new PreciseNumber((12 * i + 10) + ""))
-                        .divide(new PreciseNumber(Math.pow(i + 1, 3) + ""));
-                L = L.add(lSummand);
-                X = X.multiply(xMultiplier);
-                sum = sum.add(M.multiply(L).divide(X));
-            }
-            return C.divide(sum);
-        }
-    };
-    /**
-     * Stores objects of NumberInterface with integer values for reuse.
-     */
-    private final static HashMap<Class<? extends NumberInterface>, HashMap<Integer, NumberInterface>> integerValues = new HashMap<>();
-    /**
-     * The division operator, /
-     */
-    public static final NumberOperator OP_DIVIDE = new NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1) {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 2 && params[1].compareTo(fromInt(params[0].getClass(), 0)) != 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return params[0].divide(params[1]);
-        }
-    };
-    /**
-     * The factorial operator, !
-     */
-    public static final NumberOperator OP_FACTORIAL = new NumberOperator(OperatorAssociativity.RIGHT, OperatorType.UNARY_POSTFIX, 0) {
-        //private HashMap<Class<? extends NumberInterface>, ArrayList<NumberInterface>> storedList = new HashMap<Class<? extends NumberInterface>, ArrayList<NumberInterface>>();
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1
-                    && params[0].fractionalPart().compareTo(fromInt(params[0].getClass(), 0)) == 0
-                    && params[0].signum() >= 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            if (params[0].signum() == 0) {
-                return fromInt(params[0].getClass(), 1);
-            }
-            NumberInterface one = fromInt(params[0].getClass(), 1);
-            NumberInterface factorial = params[0];
-            NumberInterface multiplier = params[0];
-            //It is necessary to later prevent calls of factorial on anything but non-negative integers.
-            while ((multiplier = multiplier.subtract(one)).signum() == 1) {
-                factorial = factorial.multiply(multiplier);
-            }
-            return factorial;
-                /*if(!storedList.containsKey(params[0].getClass())){
-                    storedList.put(params[0].getClass(), new ArrayList<NumberInterface>());
-                    storedList.get(params[0].getClass()).add(NaiveNumber.ONE.promoteTo(params[0].getClass()));
-                    storedList.get(params[0].getClass()).add(NaiveNumber.ONE.promoteTo(params[0].getClass()));
-                }*/
-        }
-    };
-    /**
-     * The permutation operator.
-     */
-    public static final NumberOperator OP_NPR = new NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0) {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 2 && params[0].fractionalPart().signum() == 0
-                    && params[1].fractionalPart().signum() == 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            if (params[0].compareTo(params[1]) < 0 ||
-                    params[0].signum() < 0 ||
-                    (params[0].signum() == 0 && params[1].signum() != 0)) return fromInt(params[0].getClass(), 0);
-            NumberInterface total = fromInt(params[0].getClass(), 1);
-            NumberInterface multiplyBy = params[0];
-            NumberInterface remainingMultiplications = params[1];
-            NumberInterface halfway = params[0].divide(fromInt(params[0].getClass(), 2));
-            if (remainingMultiplications.compareTo(halfway) > 0) {
-                remainingMultiplications = params[0].subtract(remainingMultiplications);
-            }
-            while (remainingMultiplications.signum() > 0) {
-                total = total.multiply(multiplyBy);
-                remainingMultiplications = remainingMultiplications.subtract(fromInt(params[0].getClass(), 1));
-                multiplyBy = multiplyBy.subtract(fromInt(params[0].getClass(), 1));
-            }
-            return total;
-        }
-    };
-    /**
-     * The combination operator.
-     */
-    public static final NumberOperator OP_NCR = new NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0) {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 2 && params[0].fractionalPart().signum() == 0
-                    && params[1].fractionalPart().signum() == 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return OP_NPR.apply(params).divide(OP_FACTORIAL.apply(params[1]));
-        }
-    };
-    /**
-     * The absolute value function, abs(-3) = 3
-     */
-    public static final NumberFunction FUNCTION_ABS = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return params[0].multiply(fromInt(params[0].getClass(), params[0].signum()));
-        }
-    };
-    /**
-     * The natural log function.
-     */
-    public static final NumberFunction FUNCTION_LN = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1 && params[0].compareTo(fromInt(params[0].getClass(), 0)) > 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            NumberInterface param = params[0];
-            NumberInterface one = fromInt(param.getClass(), 1);
-            int powersOf2 = 0;
-            while (FUNCTION_ABS.apply(param.subtract(one)).compareTo(new NaiveNumber(0.1).promoteTo(param.getClass())) >= 0) {
-                if (param.subtract(one).signum() == 1) {
-                    param = param.divide(fromInt(param.getClass(), 2));
-                    powersOf2++;
-                    if (param.subtract(one).signum() != 1) {
-                        break;
-                        //No infinite loop for you.
-                    }
-                } else {
-                    param = param.multiply(fromInt(param.getClass(), 2));
-                    powersOf2--;
-                    if (param.subtract(one).signum() != -1) {
-                        break;
-                        //No infinite loop for you.
-                    }
-                }
-            }
-            return getLog2(param).multiply(fromInt(param.getClass(), powersOf2)).add(getLogPartialSum(param));
-        }
-
-        /**
-         * Returns the partial sum of the Taylor series for logx (around x=1).
-         * Automatically determines the number of terms needed based on the precision of x.
-         * @param x value at which the series is evaluated. 0 < x < 2. (x=2 is convergent but impractical.)
-         * @return the partial sum.
-         */
-        private NumberInterface getLogPartialSum(NumberInterface x) {
-
-            NumberInterface maxError = x.getMaxError();
-            x = x.subtract(fromInt(x.getClass(), 1)); //Terms used are for log(x+1).
-            NumberInterface currentNumerator = x, currentTerm = x, sum = x;
-            int n = 1;
-            while (FUNCTION_ABS.apply(currentTerm).compareTo(maxError) > 0) {
-                n++;
-                currentNumerator = currentNumerator.multiply(x).negate();
-                currentTerm = currentNumerator.divide(fromInt(x.getClass(), n));
-                sum = sum.add(currentTerm);
-            }
-            return sum;
-        }
-
-        /**
-         * Returns natural log of 2 to the required precision of the class of number.
-         * @param number a number of the same type as the return type. (Used for precision.)
-         * @return the value of log(2) with the appropriate precision.
-         */
-        private NumberInterface getLog2(NumberInterface number) {
-            NumberInterface maxError = number.getMaxError();
-            //NumberInterface errorBound = fromInt(number.getClass(), 1);
-            //We'll use the series \sigma_{n >= 1) ((1/3^n + 1/4^n) * 1/n)
-            //In the following, a=1/3^n, b=1/4^n, c = 1/n.
-            //a is also an error bound.
-            NumberInterface a = fromInt(number.getClass(), 1), b = a, c = a;
-            NumberInterface sum = fromInt(number.getClass(), 0);
-            NumberInterface one = fromInt(number.getClass(), 1);
-            int n = 0;
-            while (a.compareTo(maxError) >= 1) {
-                n++;
-                a = a.divide(fromInt(number.getClass(), 3));
-                b = b.divide(fromInt(number.getClass(), 4));
-                c = one.divide(fromInt(number.getClass(), n));
-                sum = sum.add(a.add(b).multiply(c));
-            }
-            return sum;
-        }
-    };
-    /**
-     * Gets a random number smaller or equal to the given number's integer value.
-     */
-    public static final NumberFunction FUNCTION_RAND_INT = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return fromInt(params[0].getClass(), (int) Math.round(Math.random() * params[0].floor().intValue()));
-        }
-    };
-    private static final HashMap<Class<? extends NumberInterface>, ArrayList<NumberInterface>> FACTORIAL_LISTS = new HashMap<>();
-    /**
-     * The exponential function, exp(1) = e^1 = 2.71...
-     */
-    public static final NumberFunction FUNCTION_EXP = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            NumberInterface maxError = params[0].getMaxError();
-            int n = 0;
-            if (params[0].signum() < 0) {
-                NumberInterface[] negatedParams = {params[0].negate()};
-                return fromInt(params[0].getClass(), 1).divide(applyInternal(negatedParams));
-            } else {
-                //We need n such that x^(n+1) * 3^ceil(x) <= maxError * (n+1)!.
-                //right and left refer to lhs and rhs in the above inequality.
-                NumberInterface sum = fromInt(params[0].getClass(), 1);
-                NumberInterface nextNumerator = params[0];
-                NumberInterface left = params[0].multiply(fromInt(params[0].getClass(), 3).intPow(params[0].ceiling().intValue())), right = maxError;
-                do {
-                    sum = sum.add(nextNumerator.divide(factorial(params[0].getClass(), n + 1)));
-                    n++;
-                    nextNumerator = nextNumerator.multiply(params[0]);
-                    left = left.multiply(params[0]);
-                    NumberInterface nextN = fromInt(params[0].getClass(), n + 1);
-                    right = right.multiply(nextN);
-                    //System.out.println(left + ", " + right);
-                }
-                while (left.compareTo(right) > 0);
-                //System.out.println(n+1);
-                return sum;
-            }
-        }
-    };
-    /**
-     * The caret / pow operator, ^
-     */
-    public static final NumberOperator OP_CARET = new NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 2) {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            NumberInterface zero = fromInt(params[0].getClass(), 0);
-            return params.length == 2
-                    && !(params[0].compareTo(zero) == 0
-                    && params[1].compareTo(zero) == 0)
-                    && !(params[0].signum() == -1 && params[1].fractionalPart().compareTo(zero) != 0);
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            NumberInterface zero = fromInt(params[0].getClass(), 0);
-            if (params[0].compareTo(zero) == 0)
-                return zero;
-            else if (params[1].compareTo(zero) == 0)
-                return fromInt(params[0].getClass(), 1);
-            //Detect integer bases:
-            if (params[0].fractionalPart().compareTo(fromInt(params[0].getClass(), 0)) == 0
-                    && FUNCTION_ABS.apply(params[1]).compareTo(fromInt(params[0].getClass(), Integer.MAX_VALUE)) < 0
-                    && FUNCTION_ABS.apply(params[1]).compareTo(fromInt(params[1].getClass(), 1)) >= 0) {
-                NumberInterface[] newParams = {params[0], params[1].fractionalPart()};
-                return params[0].intPow(params[1].floor().intValue()).multiply(applyInternal(newParams));
-            }
-            return FUNCTION_EXP.apply(FUNCTION_LN.apply(FUNCTION_ABS.apply(params[0])).multiply(params[1]));
-        }
-    };
-    /**
-     * The sine function (the argument is interpreted in radians).
-     */
-    public final NumberFunction functionSin = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            NumberInterface pi = piFor(params[0].getClass());
-            NumberInterface twoPi = pi.multiply(fromInt(pi.getClass(), 2));
-            NumberInterface theta = getSmallAngle(params[0], pi);
-            //System.out.println(theta);
-            if (theta.compareTo(pi.multiply(new NaiveNumber(1.5).promoteTo(twoPi.getClass()))) >= 0) {
-                theta = theta.subtract(twoPi);
-            } else if (theta.compareTo(pi.divide(fromInt(pi.getClass(), 2))) > 0) {
-                theta = pi.subtract(theta);
-            }
-            //System.out.println(theta);
-            return sinTaylor(theta);
-        }
-    };
-    /**
-     * The cosine function (the argument is in radians).
-     */
-    public final NumberFunction functionCos = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return functionSin.apply(piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
-                    .subtract(params[0]));
-        }
-    };
-    /**
-     * The tangent function (the argument is in radians).
-     */
-    public final NumberFunction functionTan = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return functionSin.apply(params[0]).divide(functionCos.apply(params[0]));
-        }
-    };
-    /**
-     * The secant function (the argument is in radians).
-     */
-    public final NumberFunction functionSec = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return fromInt(params[0].getClass(), 1).divide(functionCos.apply(params[0]));
-        }
-    };
-    /**
-     * The cosecant function (the argument is in radians).
-     */
-    public final NumberFunction functionCsc = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return fromInt(params[0].getClass(), 1).divide(functionSin.apply(params[0]));
-        }
-    };
-    /**
-     * The cotangent function (the argument is in radians).
-     */
-    public final NumberFunction functionCot = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return functionCos.apply(params[0]).divide(functionSin.apply(params[0]));
-        }
-    };
-
-    /**
-     * The arcsine function (return type in radians).
-     */
-    public final NumberFunction functionArcsin = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1
-                    && FUNCTION_ABS.apply(params[0]).compareTo(fromInt(params[0].getClass(), 1)) <= 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            if (FUNCTION_ABS.apply(params[0]).compareTo(new NaiveNumber(0.8).promoteTo(params[0].getClass())) >= 0) {
-                NumberInterface[] newParams = {FUNCTION_SQRT.apply(fromInt(params[0].getClass(), 1).subtract(params[0].multiply(params[0])))};
-                return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
-                        .subtract(applyInternal(newParams)).multiply(fromInt(params[0].getClass(), params[0].signum()));
-            }
-            NumberInterface currentTerm = params[0], sum = currentTerm,
-                    multiplier = currentTerm.multiply(currentTerm), summandBound = sum.getMaxError().multiply(fromInt(sum.getClass(), 1).subtract(multiplier)),
-                    power = currentTerm, coefficient = fromInt(params[0].getClass(), 1);
-            int exponent = 1;
-            while (FUNCTION_ABS.apply(currentTerm).compareTo(summandBound) > 0) {
-                exponent += 2;
-                power = power.multiply(multiplier);
-                coefficient = coefficient.multiply(fromInt(params[0].getClass(), exponent - 2))
-                        .divide(fromInt(params[0].getClass(), exponent - 1));
-                currentTerm = power.multiply(coefficient).divide(fromInt(power.getClass(), exponent));
-                sum = sum.add(currentTerm);
-            }
-            return sum;
-        }
-    };
-
-    /**
-     * The arccosine function.
-     */
-    public final NumberFunction functionArccos = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1 && FUNCTION_ABS.apply(params[0]).compareTo(fromInt(params[0].getClass(), 1)) <= 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
-                    .subtract(functionArcsin.apply(params));
-        }
-    };
-
-    /**
-     * The arccosecant function.
-     */
-    public final NumberFunction functionArccsc = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1 && FUNCTION_ABS.apply(params[0]).compareTo(fromInt(params[0].getClass(), 1)) >= 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            NumberInterface[] reciprocalParamArr = {fromInt(params[0].getClass(), 1).divide(params[0])};
-            return functionArcsin.apply(reciprocalParamArr);
-        }
-    };
-
-    /**
-     * The arcsecant function.
-     */
-    public final NumberFunction functionArcsec = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1 && FUNCTION_ABS.apply(params[0]).compareTo(fromInt(params[0].getClass(), 1)) >= 0;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            NumberInterface[] reciprocalParamArr = {fromInt(params[0].getClass(), 1).divide(params[0])};
-            return functionArccos.apply(reciprocalParamArr);
-        }
-    };
-
-    /**
-     * The arctangent function.
-     */
-    public final NumberFunction functionArctan = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            if (params[0].signum() == -1) {
-                NumberInterface[] negatedParams = {params[0].negate()};
-                return applyInternal(negatedParams).negate();
-            }
-            if (params[0].compareTo(fromInt(params[0].getClass(), 1)) > 0) {
-                NumberInterface[] reciprocalParams = {fromInt(params[0].getClass(), 1).divide(params[0])};
-                return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
-                        .subtract(applyInternal(reciprocalParams));
-            }
-            if (params[0].compareTo(fromInt(params[0].getClass(), 1)) == 0) {
-                return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 4));
-            }
-            if (params[0].compareTo(new NaiveNumber(0.9).promoteTo(params[0].getClass())) >= 0) {
-                NumberInterface[] newParams = {params[0].multiply(fromInt(params[0].getClass(), 2))
-                        .divide(fromInt(params[0].getClass(), 1).subtract(params[0].multiply(params[0])))};
-                return applyInternal(newParams).divide(fromInt(params[0].getClass(), 2));
-            }
-            NumberInterface currentPower = params[0], currentTerm = currentPower, sum = currentTerm,
-                    maxError = params[0].getMaxError(), multiplier = currentPower.multiply(currentPower).negate();
-            int n = 1;
-            while (FUNCTION_ABS.apply(currentTerm).compareTo(maxError) > 0) {
-                n += 2;
-                currentPower = currentPower.multiply(multiplier);
-                currentTerm = currentPower.divide(fromInt(currentPower.getClass(), n));
-                sum = sum.add(currentTerm);
-            }
-            return sum;
-        }
-    };
-
-    /**
-     * The arccotangent function. Range: (0, pi).
-     */
-    public final NumberFunction functionArccot = new NumberFunction() {
-        @Override
-        public boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
-        }
-
-        @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
-            return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
-                    .subtract(functionArctan.apply(params));
-        }
-    };
-
-    public StandardPlugin(PluginManager manager) {
-        super(manager);
-    }
-
-    /**
-     * Returns a partial sum of a series whose terms are given by the nthTermFunction, evaluated at x.
-     *
-     * @param x               the value at which the series is evaluated.
-     * @param nthTermFunction the function that returns the nth term of the series, in the format term(x, n).
-     * @param n               the number of terms in the partial sum.
-     * @return the value of the partial sum that has the same class as x.
-     */
-    private static NumberInterface sumSeries(NumberInterface x, BiFunction<Integer, NumberInterface, NumberInterface> nthTermFunction, int n) {
-        NumberInterface sum = fromInt(x.getClass(), 0);
-        for (int i = 0; i <= n; i++) {
-            sum = sum.add(nthTermFunction.apply(i, x));
-        }
-        return sum;
-    }
-
-    /**
-     * A factorial function that uses memoization for each number class; it efficiently
-     * computes factorials of non-negative integers.
-     *
-     * @param numberClass type of number to return.
-     * @param n           non-negative integer.
-     * @return a number of numClass with value n factorial.
-     */
-    public static NumberInterface factorial(Class<? extends NumberInterface> numberClass, int n) {
-        if (!FACTORIAL_LISTS.containsKey(numberClass)) {
-            FACTORIAL_LISTS.put(numberClass, new ArrayList<>());
-            FACTORIAL_LISTS.get(numberClass).add(fromInt(numberClass, 1));
-            FACTORIAL_LISTS.get(numberClass).add(fromInt(numberClass, 1));
-        }
-        ArrayList<NumberInterface> list = FACTORIAL_LISTS.get(numberClass);
-        if (n >= list.size()) {
-            while (list.size() < n + 16) {
-                list.add(list.get(list.size() - 1).multiply(fromInt(numberClass, list.size())));
-            }
-        }
-        return list.get(n);
-    }
-
-    /**
-     * Returns the value of the Taylor series for sin (centered at 0) at x.
-     *
-     * @param x where the series is evaluated.
-     * @return the value of the series
-     */
-    private static NumberInterface sinTaylor(NumberInterface x) {
-        NumberInterface power = x, multiplier = x.multiply(x).negate(), currentTerm = x, sum = x;
-        NumberInterface maxError = x.getMaxError();
-        int n = 1;
-        do {
-            n += 2;
-            power = power.multiply(multiplier);
-            currentTerm = power.divide(factorial(x.getClass(), n));
-            sum = sum.add(currentTerm);
-        } while (FUNCTION_ABS.apply(currentTerm).compareTo(maxError) > 0);
-        return sum;
-    }
-
-    /**
-     * Returns an equivalent angle in the interval [0, 2pi)
-     *
-     * @param phi an angle (in radians).
-     * @return theta in [0, 2pi) that differs from phi by a multiple of 2pi.
-     */
-    private static NumberInterface getSmallAngle(NumberInterface phi, NumberInterface pi) {
-        NumberInterface twoPi = pi.multiply(fromInt(pi.getClass(), 2));
-        NumberInterface theta = FUNCTION_ABS.apply(phi).subtract(twoPi
-                .multiply(FUNCTION_ABS.apply(phi).divide(twoPi).floor())); //Now theta is in [0, 2pi).
-        if (phi.signum() < 0) {
-            theta = twoPi.subtract(theta);
-        }
-        return theta;
-    }
-
-    /**
-     * Returns a number of class numType with value n.
-     *
-     * @param numType class of number to return.
-     * @param n       value of returned number.
-     * @return numClass instance with value n.
-     */
-    private static NumberInterface fromInt(Class<? extends NumberInterface> numType, int n) {
-        if (!integerValues.containsKey(numType)) {
-            integerValues.put(numType, new HashMap<>());
-        }
-        if (!integerValues.get(numType).containsKey(n)) {
-            integerValues.get(numType).put(n, new NaiveNumber(n).promoteTo(numType));
-        }
-        return integerValues.get(numType).get(n);
-    }
-
-    @Override
-    public void onEnable() {
-        registerNumberImplementation("naive", IMPLEMENTATION_NAIVE);
-        registerNumberImplementation("precise", IMPLEMENTATION_PRECISE);
-
-        registerOperator("+", OP_ADD);
-        registerOperator("-", OP_SUBTRACT);
-        registerOperator("`", OP_NEGATE);
-        registerOperator("*", OP_MULTIPLY);
-        registerOperator("/", OP_DIVIDE);
-        registerOperator("^", OP_CARET);
-        registerOperator("!", OP_FACTORIAL);
-
-        registerOperator("nPr", OP_NPR);
-        registerOperator("nCr", OP_NCR);
-
-        registerFunction("abs", FUNCTION_ABS);
-        registerFunction("exp", FUNCTION_EXP);
-        registerFunction("ln", FUNCTION_LN);
-        registerFunction("sqrt", FUNCTION_SQRT);
-
-        registerFunction("sin", functionSin);
-        registerFunction("cos", functionCos);
-        registerFunction("tan", functionTan);
-        registerFunction("sec", functionSec);
-        registerFunction("csc", functionCsc);
-        registerFunction("cot", functionCot);
-
-        registerFunction("arcsin", functionArcsin);
-        registerFunction("arccos", functionArccos);
-        registerFunction("arctan", functionArctan);
-        registerFunction("arcsec", functionArcsec);
-        registerFunction("arccsc", functionArccsc);
-        registerFunction("arccot", functionArccot);
-
-        registerFunction("random_int", FUNCTION_RAND_INT);
-
-        registerDocumentation(new Documentation("abs", "Absolute Value", "Finds the distance " +
-                "from zero of a number.", "Given a number, this function finds the distance form " +
-                "zero of a number, effectively turning negative numbers into positive ones.\n\n" +
-                "Example: abs(-2) -> 2", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("exp", "Exponentiate", "Brings e to the given power.",
-                "This function evaluates e to the power of the given value, and is the inverse " +
-                        "of the natural logarithm.\n\n" +
-                        "Example: exp(1) -> 2.718...", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("ln", "Natural Logarithm", "Gets the natural " +
-                "logarithm of the given value.", "The natural logarithm of a number is " +
-                "the power that e has to be brought to to be equal to the number.\n\n" +
-                "Example: ln(2.718) -> 1", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("sqrt", "Square Root", "Finds the square root " +
-                "of the number.", "A square root a of a number is defined as the non-negative a such that a times a is equal " +
-                "to that number.\n\n" +
-                "Example: sqrt(4) -> 2", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("sin", "Sine", "Computes the sine of the given angle, " +
-                "in radians.", "Example: sin(pi/6) -> 0.5", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("cos", "Cosine", "Computes the cosine of the given angle, " +
-                "in radians.", "Example: cos(pi/6) -> 0.866... (the exact result is sqrt(3)/2)", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("tan", "Tangent", "Computes the tangent of the given angle, " +
-                "in radians.", "Example: tan(pi/6) -> 0.577... (the exact result is 1/sqrt(3))", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("sec", "Secant", "Computes the secant of the given angle, " +
-                "in radians.", "Example: sec(pi/6) -> 1.154... (the exact result is 2/sqrt(3))", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("csc", "Cosecant", "Computes the cosecant of the given angle, " +
-                "in radians.", "Example: csc(pi/6) -> 2", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("cot", "Cotangent", "Computes the cotangent of the given angle, " +
-                "in radians.", "Example: cot(pi/6) -> 1.732... (the exact result is sqrt(3))", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("random_int", "Random Integer", "Generates a random integer [0, n].",
-                "Generates a pseudorandom number using the standard JVM random mechanism, keeping it less than or " +
-                        "equal to the given number.\n\n" +
-                        "Example: random_int(5) -> 4\n" +
-                        "random_int(5) -> 3\n" +
-                        "random_int(5) -> 3\n", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("arcsin", "Arcsine", "Computes the arcsine of x. (The result is in radians.)",
-                "Example: arcsin(0.5) -> 0.523... (the exact result is pi/6)", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("arccos", "Arccosine", "Computes the arccosine of x. (The result is in radians.)",
-                "Example: arccos(0.5) -> 1.047... (the exact result is pi/3)", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("arctan", "Arctangent", "Computes the arctangent of x. (The result is in radians.)",
-                "Example: arctan(1) -> 0.785... (the exact result is pi/4)", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("arcsec", "Arcsecant", "Computes the arcsecant of x. (The result is in radians.)",
-                "Example: arcsec(2) -> 1.047... (the exact result is pi/3)", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("arccsc", "Arccosecant", "Computes the arcscosecant of x. (The result is in radians.)",
-                "Example: arccsc(2) -> 0.523... (the exact result is pi/6)", DocumentationType.FUNCTION));
-        registerDocumentation(new Documentation("arccot", "Arccotangent", "Computes the arccotangent of x. (The result is in radians," +
-                " in the range (0, pi).)",
-                "Example: arccot(0) -> 1.570... (the exact result is pi/2)", DocumentationType.FUNCTION));
-    }
-
-    @Override
-    public void onDisable() {
-
-    }
-}

core/src/main/java/org/nwapw/abacus/plugin/standard/StandardPlugin.java

@@ -0,0 +1,674 @@
+package org.nwapw.abacus.plugin.standard;
+
+import org.nwapw.abacus.context.MutableEvaluationContext;
+import org.nwapw.abacus.function.*;
+import org.nwapw.abacus.function.interfaces.NumberFunction;
+import org.nwapw.abacus.function.interfaces.NumberOperator;
+import org.nwapw.abacus.function.interfaces.TreeValueOperator;
+import org.nwapw.abacus.number.standard.NaiveNumber;
+import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.number.standard.PreciseNumber;
+import org.nwapw.abacus.plugin.NumberImplementation;
+import org.nwapw.abacus.plugin.Plugin;
+import org.nwapw.abacus.plugin.PluginManager;
+import org.nwapw.abacus.plugin.standard.operator.*;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+
+/**
+ * The plugin providing standard functions such as addition and subtraction to
+ * the calculator.
+ */
+public class StandardPlugin extends Plugin {
+
+    /**
+     * The set operator.
+     */
+    public static final TreeValueOperator OP_SET = new OperatorSet();
+    /**
+     * The define operator.
+     */
+    public final TreeValueOperator OP_DEFINE = new OperatorDefine();
+    /**
+     * The addition operator, +
+     */
+    public static final NumberOperator OP_ADD = new OperatorAdd();
+    /**
+     * The subtraction operator, -
+     */
+    public static final NumberOperator OP_SUBTRACT = new OperatorSubtract();
+    /**
+     * The negation operator, -
+     */
+    public static final NumberOperator OP_NEGATE = new OperatorNegate();
+    /**
+     * The multiplication operator, *
+     */
+    public static final NumberOperator OP_MULTIPLY = new OperatorMultiply();
+    /**
+     * The implementation for double-based naive numbers.
+     */
+    public static final NumberImplementation IMPLEMENTATION_NAIVE = new NumberImplementation(NaiveNumber.class, 0) {
+        @Override
+        public NumberInterface instanceForString(String string) {
+            return new NaiveNumber(string);
+        }
+
+        @Override
+        public NumberInterface instanceForPi() {
+            return new NaiveNumber(Math.PI);
+        }
+    };
+    /**
+     * The implementation for the infinite-precision BigDecimal.
+     */
+    public static final NumberImplementation IMPLEMENTATION_PRECISE = new NumberImplementation(PreciseNumber.class, 0) {
+        @Override
+        public NumberInterface instanceForString(String string) {
+            return new PreciseNumber(string);
+        }
+
+        @Override
+        public NumberInterface instanceForPi() {
+            MutableEvaluationContext dummyContext = new MutableEvaluationContext(null, this, null);
+            NumberInterface C = FUNCTION_SQRT.apply(dummyContext, new PreciseNumber("10005")).multiply(new PreciseNumber("426880"));
+            NumberInterface M = PreciseNumber.ONE;
+            NumberInterface L = new PreciseNumber("13591409");
+            NumberInterface X = M;
+            NumberInterface sum = L;
+            int termsNeeded = C.getMaxPrecision() / 13 + 1;
+
+            NumberInterface lSummand = new PreciseNumber("545140134");
+            NumberInterface xMultiplier = new PreciseNumber("262537412")
+                    .multiply(new PreciseNumber("1000000000"))
+                    .add(new PreciseNumber("640768000"))
+                    .negate();
+            for (int i = 0; i < termsNeeded; i++) {
+                M = M
+                        .multiply(new PreciseNumber((12 * i + 2) + ""))
+                        .multiply(new PreciseNumber((12 * i + 6) + ""))
+                        .multiply(new PreciseNumber((12 * i + 10) + ""))
+                        .divide(new PreciseNumber(Math.pow(i + 1, 3) + ""));
+                L = L.add(lSummand);
+                X = X.multiply(xMultiplier);
+                sum = sum.add(M.multiply(L).divide(X));
+            }
+            return C.divide(sum);
+        }
+    };
+    /**
+     * The division operator, /
+     */
+    public static final NumberOperator OP_DIVIDE = new OperatorDivide();
+    /**
+     * The factorial operator, !
+     */
+    public static final NumberOperator OP_FACTORIAL = new OperatorFactorial();
+    /**
+     * The permutation operator.
+     */
+    public static final NumberOperator OP_NPR = new OperatorNpr();
+    /**
+     * The combination operator.
+     */
+    public static final NumberOperator OP_NCR = new OperatorNcr();
+    /**
+     * The absolute value function, abs(-3) = 3
+     */
+    public static final NumberFunction FUNCTION_ABS = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return params[0].multiply(context.getInheritedNumberImplementation().instanceForString(Integer.toString(params[0].signum())));
+        }
+    };
+    /**
+     * The natural log function.
+     */
+    public static final NumberFunction FUNCTION_LN = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1 && params[0].compareTo(context.getInheritedNumberImplementation().instanceForString("0")) > 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            NumberImplementation implementation = context.getInheritedNumberImplementation();
+            NumberInterface param = params[0];
+            NumberInterface one = implementation.instanceForString("1");
+            int powersOf2 = 0;
+            while (FUNCTION_ABS.apply(context, param.subtract(one)).compareTo(implementation.instanceForString(".1")) >= 0) {
+                if (param.subtract(one).signum() == 1) {
+                    param = param.divide(implementation.instanceForString("2"));
+                    powersOf2++;
+                    if (param.subtract(one).signum() != 1) {
+                        break;
+                        //No infinite loop for you.
+                    }
+                } else {
+                    param = param.multiply(implementation.instanceForString("2"));
+                    powersOf2--;
+                    if (param.subtract(one).signum() != -1) {
+                        break;
+                        //No infinite loop for you.
+                    }
+                }
+            }
+            return getLog2(context.getInheritedNumberImplementation(), param).multiply(implementation.instanceForString(Integer.toString(powersOf2))).add(getLogPartialSum(context, param));
+        }
+
+        /**
+         * Returns the partial sum of the Taylor series for logx (around x=1).
+         * Automatically determines the number of terms needed based on the precision of x.
+         * @param x value at which the series is evaluated. 0 < x < 2. (x=2 is convergent but impractical.)
+         * @return the partial sum.
+         */
+        private NumberInterface getLogPartialSum(MutableEvaluationContext context, NumberInterface x) {
+            NumberImplementation implementation = context.getInheritedNumberImplementation();
+            NumberInterface maxError = x.getMaxError();
+            x = x.subtract(implementation.instanceForString("1")); //Terms used are for log(x+1).
+            NumberInterface currentNumerator = x, currentTerm = x, sum = x;
+            int n = 1;
+            while (FUNCTION_ABS.apply(context, currentTerm).compareTo(maxError) > 0) {
+                n++;
+                currentNumerator = currentNumerator.multiply(x).negate();
+                currentTerm = currentNumerator.divide(implementation.instanceForString(Integer.toString(n)));
+                sum = sum.add(currentTerm);
+            }
+            return sum;
+        }
+
+        /**
+         * Returns natural log of 2 to the required precision of the class of number.
+         * @param number a number of the same type as the return type. (Used for precision.)
+         * @return the value of log(2) with the appropriate precision.
+         */
+        private NumberInterface getLog2(NumberImplementation implementation, NumberInterface number) {
+            NumberInterface maxError = number.getMaxError();
+            //NumberInterface errorBound = implementation.instanceForString("1");
+            //We'll use the series \sigma_{n >= 1) ((1/3^n + 1/4^n) * 1/n)
+            //In the following, a=1/3^n, b=1/4^n, c = 1/n.
+            //a is also an error bound.
+            NumberInterface a = implementation.instanceForString("1"), b = a, c;
+            NumberInterface sum = implementation.instanceForString("0");
+            NumberInterface one = implementation.instanceForString("1");
+            int n = 0;
+            while (a.compareTo(maxError) >= 1) {
+                n++;
+                a = a.divide(implementation.instanceForString("3"));
+                b = b.divide(implementation.instanceForString("4"));
+                c = one.divide(implementation.instanceForString(Integer.toString(n)));
+                sum = sum.add(a.add(b).multiply(c));
+            }
+            return sum;
+        }
+    };
+    /**
+     * Gets a random number smaller or equal to the given number's integer value.
+     */
+    public static final NumberFunction FUNCTION_RAND_INT = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return context.getInheritedNumberImplementation().instanceForString(Long.toString(Math.round(Math.random() * params[0].floor().intValue())));
+        }
+    };
+    /**
+     * The caret / pow operator, ^
+     */
+    public static final NumberOperator OP_CARET = new OperatorCaret();
+    /**
+     * The square root function.
+     */
+    public static final NumberFunction FUNCTION_SQRT = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return OP_CARET.apply(context, params[0], context.getInheritedNumberImplementation().instanceForString(".5"));
+        }
+    };
+    private static final HashMap<NumberImplementation, ArrayList<NumberInterface>> FACTORIAL_LISTS = new HashMap<>();
+    /**
+     * The exponential function, exp(1) = e^1 = 2.71...
+     */
+    public static final NumberFunction FUNCTION_EXP = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            NumberImplementation implementation = context.getInheritedNumberImplementation();
+            NumberInterface maxError = params[0].getMaxError();
+            int n = 0;
+            if (params[0].signum() < 0) {
+                NumberInterface[] negatedParams = {params[0].negate()};
+                return implementation.instanceForString("1").divide(applyInternal(context, negatedParams));
+            } else {
+                //We need n such that x^(n+1) * 3^ceil(x) <= maxError * (n+1)!.
+                //right and left refer to lhs and rhs in the above inequality.
+                NumberInterface sum = implementation.instanceForString("1");
+                NumberInterface nextNumerator = params[0];
+                NumberInterface left = params[0].multiply(implementation.instanceForString("3").intPow(params[0].ceiling().intValue())), right = maxError;
+                do {
+                    sum = sum.add(nextNumerator.divide(factorial(implementation, n + 1)));
+                    n++;
+                    nextNumerator = nextNumerator.multiply(params[0]);
+                    left = left.multiply(params[0]);
+                    NumberInterface nextN = implementation.instanceForString(Integer.toString(n + 1));
+                    right = right.multiply(nextN);
+                    //System.out.println(left + ", " + right);
+                }
+                while (left.compareTo(right) > 0);
+                //System.out.println(n+1);
+                return sum;
+            }
+        }
+    };
+    /**
+     * The sine function (the argument is interpreted in radians).
+     */
+    public final NumberFunction functionSin = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            NumberImplementation implementation = context.getInheritedNumberImplementation();
+            NumberInterface pi = piFor(params[0].getClass());
+            NumberInterface twoPi = pi.multiply(implementation.instanceForString("2"));
+            NumberInterface theta = getSmallAngle(context, params[0], pi);
+            //System.out.println(theta);
+            if (theta.compareTo(pi.multiply(implementation.instanceForString("1.5"))) >= 0) {
+                theta = theta.subtract(twoPi);
+            } else if (theta.compareTo(pi.divide(implementation.instanceForString("2"))) > 0) {
+                theta = pi.subtract(theta);
+            }
+            //System.out.println(theta);
+            return sinTaylor(context, theta);
+        }
+    };
+    /**
+     * The cosine function (the argument is in radians).
+     */
+    public final NumberFunction functionCos = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return functionSin.apply(context, piFor(params[0].getClass()).divide(context.getInheritedNumberImplementation().instanceForString("2"))
+                    .subtract(params[0]));
+        }
+    };
+    /**
+     * The tangent function (the argument is in radians).
+     */
+    public final NumberFunction functionTan = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return functionSin.apply(context, params[0]).divide(functionCos.apply(context, params[0]));
+        }
+    };
+    /**
+     * The secant function (the argument is in radians).
+     */
+    public final NumberFunction functionSec = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return context.getInheritedNumberImplementation().instanceForString("1").divide(functionCos.apply(context, params[0]));
+        }
+    };
+    /**
+     * The cosecant function (the argument is in radians).
+     */
+    public final NumberFunction functionCsc = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return context.getInheritedNumberImplementation().instanceForString("1").divide(functionSin.apply(context, params[0]));
+        }
+    };
+    /**
+     * The cotangent function (the argument is in radians).
+     */
+    public final NumberFunction functionCot = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return functionCos.apply(context, params[0]).divide(functionSin.apply(context, params[0]));
+        }
+    };
+
+    /**
+     * The arcsine function (return type in radians).
+     */
+    public final NumberFunction functionArcsin = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1
+                    && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) <= 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            NumberImplementation implementation = context.getInheritedNumberImplementation();
+            if (FUNCTION_ABS.apply(context, params[0]).compareTo(implementation.instanceForString(".8")) >= 0) {
+                NumberInterface[] newParams = {FUNCTION_SQRT.apply(context, implementation.instanceForString("1").subtract(params[0].multiply(params[0])))};
+                return piFor(params[0].getClass()).divide(implementation.instanceForString("2"))
+                        .subtract(applyInternal(context, newParams)).multiply(implementation.instanceForString(Integer.toString(params[0].signum())));
+            }
+            NumberInterface currentTerm = params[0], sum = currentTerm,
+                    multiplier = currentTerm.multiply(currentTerm), summandBound = sum.getMaxError().multiply(implementation.instanceForString("1").subtract(multiplier)),
+                    power = currentTerm, coefficient = implementation.instanceForString("1");
+            int exponent = 1;
+            while (FUNCTION_ABS.apply(context, currentTerm).compareTo(summandBound) > 0) {
+                exponent += 2;
+                power = power.multiply(multiplier);
+                coefficient = coefficient.multiply(implementation.instanceForString(Integer.toString(exponent - 2)))
+                        .divide(implementation.instanceForString(Integer.toString(exponent - 1)));
+                currentTerm = power.multiply(coefficient).divide(implementation.instanceForString(Integer.toString(exponent)));
+                sum = sum.add(currentTerm);
+            }
+            return sum;
+        }
+    };
+
+    /**
+     * The arccosine function.
+     */
+    public final NumberFunction functionArccos = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) <= 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return piFor(params[0].getClass()).divide(context.getInheritedNumberImplementation().instanceForString("2"))
+                    .subtract(functionArcsin.apply(context, params));
+        }
+    };
+
+    /**
+     * The arccosecant function.
+     */
+    public final NumberFunction functionArccsc = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) >= 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            NumberInterface[] reciprocalParamArr = {context.getInheritedNumberImplementation().instanceForString("1").divide(params[0])};
+            return functionArcsin.apply(context, reciprocalParamArr);
+        }
+    };
+
+    /**
+     * The arcsecant function.
+     */
+    public final NumberFunction functionArcsec = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) >= 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            NumberInterface[] reciprocalParamArr = {context.getInheritedNumberImplementation().instanceForString("1").divide(params[0])};
+            return functionArccos.apply(context, reciprocalParamArr);
+        }
+    };
+
+    /**
+     * The arctangent function.
+     */
+    public final NumberFunction functionArctan = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            NumberImplementation implementation = context.getInheritedNumberImplementation();
+            if (params[0].signum() == -1) {
+                NumberInterface[] negatedParams = {params[0].negate()};
+                return applyInternal(context, negatedParams).negate();
+            }
+            if (params[0].compareTo(implementation.instanceForString("1")) > 0) {
+                NumberInterface[] reciprocalParams = {implementation.instanceForString("1").divide(params[0])};
+                return piFor(params[0].getClass()).divide(implementation.instanceForString("2"))
+                        .subtract(applyInternal(context, reciprocalParams));
+            }
+            if (params[0].compareTo(implementation.instanceForString("1")) == 0) {
+                return piFor(params[0].getClass()).divide(implementation.instanceForString("4"));
+            }
+            if (params[0].compareTo(implementation.instanceForString(".9")) >= 0) {
+                NumberInterface[] newParams = {params[0].multiply(implementation.instanceForString("2"))
+                        .divide(implementation.instanceForString("1").subtract(params[0].multiply(params[0])))};
+                return applyInternal(context, newParams).divide(implementation.instanceForString("2"));
+            }
+            NumberInterface currentPower = params[0], currentTerm = currentPower, sum = currentTerm,
+                    maxError = params[0].getMaxError(), multiplier = currentPower.multiply(currentPower).negate();
+            int n = 1;
+            while (FUNCTION_ABS.apply(context, currentTerm).compareTo(maxError) > 0) {
+                n += 2;
+                currentPower = currentPower.multiply(multiplier);
+                currentTerm = currentPower.divide(implementation.instanceForString(Integer.toString(n)));
+                sum = sum.add(currentTerm);
+            }
+            return sum;
+        }
+    };
+
+    /**
+     * The arccotangent function. Range: (0, pi).
+     */
+    public final NumberFunction functionArccot = new NumberFunction() {
+        @Override
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+            return piFor(params[0].getClass()).divide(context.getInheritedNumberImplementation().instanceForString("2"))
+                    .subtract(functionArctan.apply(context, params));
+        }
+    };
+
+    public StandardPlugin(PluginManager manager) {
+        super(manager);
+    }
+
+    /**
+     * A factorial function that uses memoization for each number class; it efficiently
+     * computes factorials of non-negative integers.
+     *
+     * @param implementation type of number to return.
+     * @param n              non-negative integer.
+     * @return a number of numClass with value n factorial.
+     */
+    synchronized public static NumberInterface factorial(NumberImplementation implementation, int n) {
+        if (!FACTORIAL_LISTS.containsKey(implementation)) {
+            FACTORIAL_LISTS.put(implementation, new ArrayList<>());
+            FACTORIAL_LISTS.get(implementation).add(implementation.instanceForString("1"));
+            FACTORIAL_LISTS.get(implementation).add(implementation.instanceForString("1"));
+        }
+        ArrayList<NumberInterface> list = FACTORIAL_LISTS.get(implementation);
+        if (n >= list.size()) {
+            while (list.size() < n + 16) {
+                list.add(list.get(list.size() - 1).multiply(implementation.instanceForString(Integer.toString(list.size()))));
+            }
+        }
+        return list.get(n);
+    }
+
+    /**
+     * Returns the value of the Taylor series for sin (centered at 0) at x.
+     *
+     * @param x where the series is evaluated.
+     * @return the value of the series
+     */
+    private static NumberInterface sinTaylor(MutableEvaluationContext context, NumberInterface x) {
+        NumberInterface power = x, multiplier = x.multiply(x).negate(), currentTerm, sum = x;
+        NumberInterface maxError = x.getMaxError();
+        int n = 1;
+        do {
+            n += 2;
+            power = power.multiply(multiplier);
+            currentTerm = power.divide(factorial(context.getInheritedNumberImplementation(), n));
+            sum = sum.add(currentTerm);
+        } while (FUNCTION_ABS.apply(context, currentTerm).compareTo(maxError) > 0);
+        return sum;
+    }
+
+    /**
+     * Returns an equivalent angle in the interval [0, 2pi)
+     *
+     * @param phi an angle (in radians).
+     * @return theta in [0, 2pi) that differs from phi by a multiple of 2pi.
+     */
+    private static NumberInterface getSmallAngle(MutableEvaluationContext context, NumberInterface phi, NumberInterface pi) {
+        NumberInterface twoPi = pi.multiply(context.getInheritedNumberImplementation().instanceForString("2"));
+        NumberInterface theta = FUNCTION_ABS.apply(context, phi).subtract(twoPi
+                .multiply(FUNCTION_ABS.apply(context, phi).divide(twoPi).floor())); //Now theta is in [0, 2pi).
+        if (phi.signum() < 0) {
+            theta = twoPi.subtract(theta);
+        }
+        return theta;
+    }
+
+    @Override
+    public void onEnable() {
+        registerNumberImplementation("naive", IMPLEMENTATION_NAIVE);
+        registerNumberImplementation("precise", IMPLEMENTATION_PRECISE);
+
+        registerOperator("+", OP_ADD);
+        registerOperator("-", OP_SUBTRACT);
+        registerOperator("`", OP_NEGATE);
+        registerOperator("*", OP_MULTIPLY);
+        registerOperator("/", OP_DIVIDE);
+        registerOperator("^", OP_CARET);
+        registerOperator("!", OP_FACTORIAL);
+
+        registerTreeValueOperator("=", OP_SET);
+        registerTreeValueOperator(":=", OP_DEFINE);
+
+        registerOperator("nPr", OP_NPR);
+        registerOperator("nCr", OP_NCR);
+
+        registerFunction("abs", FUNCTION_ABS);
+        registerFunction("exp", FUNCTION_EXP);
+        registerFunction("ln", FUNCTION_LN);
+        registerFunction("sqrt", FUNCTION_SQRT);
+
+        registerFunction("sin", functionSin);
+        registerFunction("cos", functionCos);
+        registerFunction("tan", functionTan);
+        registerFunction("sec", functionSec);
+        registerFunction("csc", functionCsc);
+        registerFunction("cot", functionCot);
+
+        registerFunction("arcsin", functionArcsin);
+        registerFunction("arccos", functionArccos);
+        registerFunction("arctan", functionArctan);
+        registerFunction("arcsec", functionArcsec);
+        registerFunction("arccsc", functionArccsc);
+        registerFunction("arccot", functionArccot);
+
+        registerFunction("random_int", FUNCTION_RAND_INT);
+
+        registerDocumentation(new Documentation("abs", "Absolute Value", "Finds the distance " +
+                "from zero of a number.", "Given a number, this function finds the distance form " +
+                "zero of a number, effectively turning negative numbers into positive ones.\n\n" +
+                "Example: abs(-2) -> 2", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("exp", "Exponentiate", "Brings e to the given power.",
+                "This function evaluates e to the power of the given value, and is the inverse " +
+                        "of the natural logarithm.\n\n" +
+                        "Example: exp(1) -> 2.718...", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("ln", "Natural Logarithm", "Gets the natural " +
+                "logarithm of the given value.", "The natural logarithm of a number is " +
+                "the power that e has to be brought to to be equal to the number.\n\n" +
+                "Example: ln(2.718) -> 1", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("sqrt", "Square Root", "Finds the square root " +
+                "of the number.", "A square root a of a number is defined as the non-negative a such that a times a is equal " +
+                "to that number.\n\n" +
+                "Example: sqrt(4) -> 2", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("sin", "Sine", "Computes the sine of the given angle, " +
+                "in radians.", "Example: sin(pi/6) -> 0.5", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("cos", "Cosine", "Computes the cosine of the given angle, " +
+                "in radians.", "Example: cos(pi/6) -> 0.866... (the exact result is sqrt(3)/2)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("tan", "Tangent", "Computes the tangent of the given angle, " +
+                "in radians.", "Example: tan(pi/6) -> 0.577... (the exact result is 1/sqrt(3))", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("sec", "Secant", "Computes the secant of the given angle, " +
+                "in radians.", "Example: sec(pi/6) -> 1.154... (the exact result is 2/sqrt(3))", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("csc", "Cosecant", "Computes the cosecant of the given angle, " +
+                "in radians.", "Example: csc(pi/6) -> 2", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("cot", "Cotangent", "Computes the cotangent of the given angle, " +
+                "in radians.", "Example: cot(pi/6) -> 1.732... (the exact result is sqrt(3))", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("random_int", "Random Integer", "Generates a random integer [0, n].",
+                "Generates a pseudorandom number using the standard JVM random mechanism, keeping it less than or " +
+                        "equal to the given number.\n\n" +
+                        "Example: random_int(5) -> 4\n" +
+                        "random_int(5) -> 3\n" +
+                        "random_int(5) -> 3\n", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arcsin", "Arcsine", "Computes the arcsine of x. (The result is in radians.)",
+                "Example: arcsin(0.5) -> 0.523... (the exact result is pi/6)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arccos", "Arccosine", "Computes the arccosine of x. (The result is in radians.)",
+                "Example: arccos(0.5) -> 1.047... (the exact result is pi/3)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arctan", "Arctangent", "Computes the arctangent of x. (The result is in radians.)",
+                "Example: arctan(1) -> 0.785... (the exact result is pi/4)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arcsec", "Arcsecant", "Computes the arcsecant of x. (The result is in radians.)",
+                "Example: arcsec(2) -> 1.047... (the exact result is pi/3)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arccsc", "Arccosecant", "Computes the arcscosecant of x. (The result is in radians.)",
+                "Example: arccsc(2) -> 0.523... (the exact result is pi/6)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arccot", "Arccotangent", "Computes the arccotangent of x. (The result is in radians," +
+                " in the range (0, pi).)",
+                "Example: arccot(0) -> 1.570... (the exact result is pi/2)", DocumentationType.FUNCTION));
+    }
+
+    @Override
+    public void onDisable() {
+        FACTORIAL_LISTS.clear();
+    }
+}

core/src/main/java/org/nwapw/abacus/tree/NumberReducer.java

@@ -1,76 +0,0 @@
-package org.nwapw.abacus.tree;
-
-import org.nwapw.abacus.Abacus;
-import org.nwapw.abacus.function.*;
-import org.nwapw.abacus.number.NumberInterface;
-
-/**
- * A reducer implementation that turns a tree into a single number.
- * This is not always guaranteed to work.
- */
-public class NumberReducer implements Reducer<NumberInterface> {
-
-    /**
-     * The plugin manager from which to draw the functions.
-     */
-    private Abacus abacus;
-
-    /**
-     * Creates a new number reducer.
-     *
-     * @param abacus the calculator instance.
-     */
-    public NumberReducer(Abacus abacus) {
-        this.abacus = abacus;
-    }
-
-    @Override
-    public NumberInterface reduceNode(TreeNode node, Object... children) {
-        if (node instanceof NumberNode) {
-            return abacus.numberFromString(((NumberNode) node).getNumber());
-        } else if(node instanceof VariableNode) {
-            return abacus.numberFromString("0");
-        } else if (node instanceof NumberBinaryNode) {
-            NumberInterface left = (NumberInterface) children[0];
-            NumberInterface right = (NumberInterface) children[1];
-            NumberOperator operator = abacus.getPluginManager().operatorFor(((BinaryNode) node).getOperation());
-            return operator.apply(left, right);
-        } else if (node instanceof NumberUnaryNode) {
-            NumberInterface child = (NumberInterface) children[0];
-            NumberOperator operator = abacus.getPluginManager().operatorFor(((UnaryNode) node).getOperation());
-            return operator.apply(child);
-        } else if (node instanceof FunctionNode) {
-            NumberInterface[] convertedChildren = new NumberInterface[children.length];
-            for (int i = 0; i < convertedChildren.length; i++) {
-                convertedChildren[i] = (NumberInterface) children[i];
-            }
-            NumberFunction function = abacus.getPluginManager().functionFor(((FunctionNode) node).getCallTo());
-            if (function == null) return null;
-            return function.apply(convertedChildren);
-        } else if (node instanceof TreeValueFunctionNode){
-            CallNode callNode = (CallNode) node;
-            TreeNode[] realChildren = new TreeNode[callNode.getChildren().size()];
-            for(int i = 0; i < realChildren.length; i++){
-                realChildren[i] = callNode.getChildren().get(i);
-            }
-            TreeValueFunction function =
-                    abacus.getPluginManager().treeValueFunctionFor(callNode.getCallTo());
-            if(function == null) return null;
-            return function.applyWithReducer(this, realChildren);
-        } else if (node instanceof TreeValueBinaryNode) {
-            BinaryNode binaryNode = (BinaryNode) node;
-            TreeValueOperator operator = abacus.getPluginManager()
-                    .treeValueOperatorFor(binaryNode.getOperation());
-            if(operator == null) return null;
-            return operator.applyWithReducer(this, binaryNode.getLeft(), binaryNode.getRight());
-        } else if(node instanceof TreeValueUnaryNode) {
-            UnaryNode unaryNode = (UnaryNode) node;
-            TreeValueOperator operator = abacus.getPluginManager()
-                    .treeValueOperatorFor(unaryNode.getOperation());
-            if(operator == null) return null;
-            return operator.applyWithReducer(this, unaryNode.getApplyTo());
-        }
-        return null;
-    }
-
-}

core/src/main/kotlin/org/nwapw/abacus/Abacus.kt

@@ -0,0 +1,114 @@
+package org.nwapw.abacus
+
+import org.nwapw.abacus.config.Configuration
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.context.EvaluationContext
+import org.nwapw.abacus.number.promotion.PromotionManager
+import org.nwapw.abacus.parsing.standard.LexerTokenizer
+import org.nwapw.abacus.parsing.standard.ShuntingYardParser
+import org.nwapw.abacus.parsing.TreeBuilder
+import org.nwapw.abacus.plugin.PluginManager
+import org.nwapw.abacus.plugin.standard.StandardPlugin
+import org.nwapw.abacus.tree.standard.NumberReducer
+import org.nwapw.abacus.tree.nodes.TreeNode
+
+/**
+ * Core class to handle all mathematics.
+ *
+ * The main calculator class. This is responsible
+ * for piecing together all of the components, allowing
+ * their interaction with each other.
+ *
+ * @property configuration the configuration to use.
+ */
+class Abacus(val configuration: Configuration) {
+
+    /**
+     * The tokenizer used to convert strings into tokens.
+     */
+    private val tokenizer = LexerTokenizer()
+    /**
+     * Parser the parser used to convert tokens into trees.
+     */
+    private val parser = ShuntingYardParser()
+    /**
+     * The plugin manager used to handle loading and unloading plugins.
+     */
+    val pluginManager = PluginManager(this)
+    /**
+     * The tree builder that handles the conversion of strings into trees.
+     */
+    val treeBuilder = TreeBuilder(tokenizer, parser)
+    /**
+     * The promotion manager used to convert between number implementations.
+     */
+    val promotionManager = PromotionManager(this)
+
+    /**
+     * The hidden, mutable implementation of the context.
+     */
+    private val mutableContext = MutableEvaluationContext(numberImplementation = StandardPlugin.IMPLEMENTATION_NAIVE)
+    /**
+     * The base context from which calculations are started.
+     */
+    val context: EvaluationContext
+        get() = mutableContext
+
+    init {
+        pluginManager.addListener(tokenizer)
+        pluginManager.addListener(parser)
+        pluginManager.addListener(promotionManager)
+    }
+
+    /**
+     * Reloads the Abacus core.
+     */
+    fun reload(){
+        pluginManager.reload()
+        with(mutableContext) {
+            numberImplementation = pluginManager.numberImplementationFor(configuration.numberImplementation)
+                    ?: StandardPlugin.IMPLEMENTATION_NAIVE
+            clearVariables()
+            clearDefinitions()
+        }
+    }
+    /**
+     * Merges the current context with the provided one, updating
+     * variables and the like.
+     * @param context the context to apply.
+     */
+    fun applyToContext(context: EvaluationContext){
+        mutableContext.apply(context)
+    }
+    /**
+     * Parses a string into a tree structure using the main
+     * tree builder.
+     *
+     * @param input the input string to parse
+     * @return the resulting tree, null if the tree builder or the produced tree are null.
+     */
+    fun parseString(input: String): TreeNode = treeBuilder.fromString(input)
+    /**
+     * Evaluates the given tree.
+     *
+     * @param tree the tree to reduce, must not be null.
+     * @return the evaluation result.
+     */
+    fun evaluateTree(tree: TreeNode): EvaluationResult {
+        return evaluateTreeWithContext(tree, context.mutableSubInstance())
+    }
+    /**
+     * Evaluates the given tree using a different context than
+     * the default one.
+     *
+     * @param tree the tree to reduce, must not be null.
+     * @param context the context to use for the evaluation.
+     * @return the evaluation result.
+     */
+    fun evaluateTreeWithContext(tree: TreeNode, context: MutableEvaluationContext): EvaluationResult {
+        val newReducer = NumberReducer(this, context)
+        val evaluationValue = tree.reduce(newReducer)
+        return EvaluationResult(evaluationValue, newReducer.context)
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/EvaluationResult.kt

@@ -0,0 +1,6 @@
+package org.nwapw.abacus
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.number.NumberInterface
+
+data class EvaluationResult(val value: NumberInterface, val resultingContext: MutableEvaluationContext)

core/src/main/kotlin/org/nwapw/abacus/config/Configuration.kt

@@ -0,0 +1,20 @@
+package org.nwapw.abacus.config
+
+/**
+ * A class that holds information that tells Abacus how to behave.
+ *
+ * Configuration stores information about how Abacus should behave, for
+ * instance, what number implementation it should use and what
+ * plugins should be ignored during loading.
+ *
+ * @property numberImplementation the number implementation Abacus should use for loading.
+ * @param disabledPlugins the plugins that should be disabled and not loaded by the plugin manager.
+ */
+open class Configuration(var numberImplementation: String = "<default>", disabledPlugins: Array<String> = emptyArray()) {
+
+    /**
+     * The set of disabled plugins that should be ignored by the plugin manager.
+     */
+    val disabledPlugins = disabledPlugins.toMutableSet()
+
+}

core/src/main/kotlin/org/nwapw/abacus/context/ChainAccumulateDelegate.kt

@@ -0,0 +1,26 @@
+package org.nwapw.abacus.context
+
+import kotlin.reflect.KProperty
+
+/**
+ * A delegate to accumulate a collection of elements in a [EvaluationContext] hierarchy.
+ *
+ * ChainAccumulateDelegate is similar to the [ChainSearchDelegate], however, it operates only on collections.
+ * Instead of returning the most recent collection, it merges them into a [Set].
+ *
+ * @param T the type of element in the collection.
+ * @property valueGetter the getter used to access the collection from the context.
+ */
+class ChainAccumulateDelegate<out T>(private val valueGetter: EvaluationContext.() -> Collection<T>) {
+
+    operator fun getValue(selfRef: Any, property: KProperty<*>): Set<T> {
+        val set = mutableSetOf<T>()
+        var currentRef: EvaluationContext = selfRef as? EvaluationContext ?: return set
+        while(true) {
+            set.addAll(currentRef.valueGetter())
+            currentRef = currentRef.parent ?: break
+        }
+        return set
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/context/ChainSearchDelegate.kt

@@ -0,0 +1,30 @@
+package org.nwapw.abacus.context
+
+import org.nwapw.abacus.exception.ContextException
+import kotlin.reflect.KProperty
+
+/**
+ * A delegate to search a hierarchy made up of [EvaluationContext].
+ *
+ * ChainSearchDelegate is a variable delegate written specifically for use in [EvaluationContext], because
+ * of its hierarchical structure. Variables not found in the current context are searched
+ * for in its parent, which continues recursively until the context being examined has no parent.
+ * This class assists that logic, which is commonly re-used with different variable types, by calling
+ * [valueGetter] on the current context, then its parent, etc.
+ *
+ * @param V the type of the property to search recursively.
+ * @property valueGetter the getter lambda to access the value from the context.
+ */
+class ChainSearchDelegate<out V>(private val valueGetter: EvaluationContext.() -> V?) {
+
+    operator fun getValue(selfRef: Any, property: KProperty<*>): V {
+        var currentRef = selfRef as EvaluationContext
+        var returnedValue = currentRef.valueGetter()
+        while (returnedValue == null) {
+            currentRef = currentRef.parent ?: break
+            returnedValue = currentRef.valueGetter()
+        }
+        return returnedValue ?: throw ContextException("context chain does not contain value")
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/context/EvaluationContext.kt

@@ -0,0 +1,84 @@
+package org.nwapw.abacus.context
+
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.NumberImplementation
+import org.nwapw.abacus.tree.Reducer
+import org.nwapw.abacus.tree.nodes.TreeNode
+
+/**
+ * A context for the reduction of a [org.nwapw.abacus.tree.TreeNode] into a number.
+ *
+ * The reduction context is used to carry important state information captured at the beginning
+ * of the reduction of an expression, such as the variables and the implementation in use.
+ *
+ * @property parent the parent of this context.
+ * @property numberImplementation the implementation for numbers of this context.
+ * @property reducer the reducer used by this context.
+ */
+open class EvaluationContext(val parent: EvaluationContext? = null,
+                             open val numberImplementation: NumberImplementation? = null,
+                             open val reducer: Reducer<NumberInterface>? = null) {
+
+    /**
+     * The map of variables in this context.
+     */
+    protected val variableMap = mutableMapOf<String, NumberInterface>()
+    /**
+     * The map of definitions in this context.
+     */
+    protected val definitionMap = mutableMapOf<String, TreeNode>()
+
+    /**
+     * The set of all variable names defined in this context.
+     */
+    val variables: Set<String>
+        get() = variableMap.keys
+
+    /**
+     * The set of all definition names defined in this context.
+     */
+    val definitions: Set<String>
+        get() = definitionMap.keys
+
+    /**
+     * The implementation inherited from this context's parent.
+     */
+    val inheritedNumberImplementation: NumberImplementation
+            by ChainSearchDelegate { numberImplementation }
+
+    /**
+     * The reducer inherited from this context's parent.
+     */
+    val inheritedReducer: Reducer<NumberInterface>
+            by ChainSearchDelegate { reducer }
+
+    /**
+     * The set of all variables in this context and its parents.
+     */
+    val inheritedVariables: Set<String> by ChainAccumulateDelegate { variables }
+
+    /**
+     * The set of all definition in this context and its parents.
+     */
+    val inheritedDefinitions: Set<String> by ChainAccumulateDelegate { definitions }
+
+    /**
+     * Create a new child instance of this context that is mutable.
+     * @return the new child instance.
+     */
+    fun mutableSubInstance(): MutableEvaluationContext = MutableEvaluationContext(this)
+
+    /**
+     * Gets a variable stored in this context.
+     */
+    fun getVariable(name: String): NumberInterface? {
+        return variableMap[name] ?: parent?.getVariable(name)
+    }
+    /**
+     * Gets the definition stored in this context.
+     */
+    fun getDefinition(name: String): TreeNode? {
+        return definitionMap[name] ?: parent?.getDefinition(name)
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/context/MutableEvaluationContext.kt

@@ -0,0 +1,69 @@
+package org.nwapw.abacus.context
+
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.NumberImplementation
+import org.nwapw.abacus.tree.Reducer
+import org.nwapw.abacus.tree.nodes.TreeNode
+
+/**
+ * A reduction context that is mutable.
+ * @param parent the parent of this context.
+ * @param numberImplementation the number implementation used in this context.
+ * @param reducer the reducer used in this context
+ */
+class MutableEvaluationContext(parent: EvaluationContext? = null,
+                               numberImplementation: NumberImplementation? = null,
+                               reducer: Reducer<NumberInterface>? = null) :
+        EvaluationContext(parent, numberImplementation, reducer) {
+
+    override var numberImplementation: NumberImplementation? = super.numberImplementation
+    override var reducer: Reducer<NumberInterface>? = super.reducer
+
+    /**
+     * Writes data stored in the [other] context over data stored in this one.
+     * @param other the context from which to copy data.
+     */
+    fun apply(other: EvaluationContext) {
+        if(other.numberImplementation != null) numberImplementation = other.numberImplementation
+        if(other.reducer != null) reducer = other.reducer
+        for(name in other.variables) {
+            setVariable(name, other.getVariable(name) ?: continue)
+        }
+        for(name in other.definitions) {
+            setDefinition(name, other.getDefinition(name) ?: continue)
+        }
+    }
+
+    /**
+     * Sets a variable to a certain [value].
+     * @param name the name of the variable.
+     * @param value the value of the variable.
+     */
+    fun setVariable(name: String, value: NumberInterface) {
+        variableMap[name] = value
+    }
+
+    /**
+     * Set a definition to a certain [value].
+     * @param name the name of the definition.
+     * @param value the value of the definition.
+     */
+    fun setDefinition(name: String, value: TreeNode) {
+        definitionMap[name] = value
+    }
+
+    /**
+     * Clears the variables defined in this context.
+     */
+    fun clearVariables(){
+        variableMap.clear()
+    }
+
+    /**
+     * Clears the definitions defined in this context.
+     */
+    fun clearDefinitions(){
+        definitionMap.clear()
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/function/Applicable.kt

@@ -1,4 +1,7 @@
-package org.nwapw.abacus.function.applicable
+package org.nwapw.abacus.function
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.exception.DomainException
 
 /**
  * A class that can be applied to arguments.
@@ -15,7 +18,7 @@ interface Applicable<in T : Any, out O : Any> {
      * @param params the parameter array to verify for compatibility.
      * @return whether the array can be used with applyInternal.
      */
-    fun matchesParams(params: Array<out T>): Boolean
+    fun matchesParams(context: MutableEvaluationContext, params: Array<out T>): Boolean
 
     /**
      * Applies the applicable object to the given parameters,
@@ -23,7 +26,7 @@ interface Applicable<in T : Any, out O : Any> {
      * @param params the parameters to apply to.
      * @return the result of the application.
      */
-    fun applyInternal(params: Array<out T>): O?
+    fun applyInternal(context: MutableEvaluationContext, params: Array<out T>): O
 
     /**
      * If the parameters can be used with this applicable, returns
@@ -32,9 +35,10 @@ interface Applicable<in T : Any, out O : Any> {
      * @param params the parameters to apply to.
      * @return the result of the operation, or null if parameters do not match.
      */
-    fun apply(vararg params: T): O? {
+    fun apply(context: MutableEvaluationContext, vararg params: T): O {
-        if (!matchesParams(params)) return null
+        if (!matchesParams(context, params))
-        return applyInternal(params)
+            throw DomainException("parameters do not match function requirements.")
+        return applyInternal(context, params)
     }
 
 }

core/src/main/kotlin/org/nwapw/abacus/function/applicable/ReducerApplicable.kt

@@ -1,43 +0,0 @@
-package org.nwapw.abacus.function.applicable
-
-import org.nwapw.abacus.tree.Reducer
-
-/**
- * Applicable that requires a reducer.
- *
- * ReducerApplicable slightly more specific Applicable that requires a reducer
- * to be passed to it along with the parameters.
- * @param <T> the type of the input arguments.
- * @param <O> the return type of the application.
- * @param <R> the required type of the reducer.
- */
-interface ReducerApplicable<in T : Any, out O : Any, in R : Any> {
-
-    /**
-     * Checks if this applicable can be applied to the
-     * given parameters.
-     * @param params the parameters to check.
-     */
-    fun matchesParams(params: Array<out T>): Boolean
-
-    /**
-     * Applies this applicable to the given arguments, and reducer.
-     * @param reducer the reducer to use in the application.
-     * @param params the arguments to apply to.
-     * @return the result of the application.
-     */
-    fun applyWithReducerInternal(reducer: Reducer<R>, params: Array<out T>): O?
-
-    /**
-     * Applies this applicable to the given arguments, and reducer,
-     * if the arguments and reducer are compatible with this applicable.
-     * @param reducer the reducer to use in the application.
-     * @param params the arguments to apply to.
-     * @return the result of the application, or null if the arguments are incompatible.
-     */
-    fun applyWithReducer(reducer: Reducer<R>, vararg params: T): O? {
-        if (!matchesParams(params)) return null
-        return applyWithReducerInternal(reducer, params)
-    }
-
-}

core/src/main/kotlin/org/nwapw/abacus/function/interfaces/NumberFunction.kt

@@ -1,6 +1,6 @@
-package org.nwapw.abacus.function
+package org.nwapw.abacus.function.interfaces
 
-import org.nwapw.abacus.function.applicable.Applicable
+import org.nwapw.abacus.function.Applicable
 import org.nwapw.abacus.number.NumberInterface
 
 /**

core/src/main/kotlin/org/nwapw/abacus/function/interfaces/NumberOperator.kt

@@ -1,6 +1,9 @@
-package org.nwapw.abacus.function
+package org.nwapw.abacus.function.interfaces
 
-import org.nwapw.abacus.function.applicable.Applicable
+import org.nwapw.abacus.function.Applicable
+import org.nwapw.abacus.function.Operator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
 import org.nwapw.abacus.number.NumberInterface
 
 /**

core/src/main/kotlin/org/nwapw/abacus/function/interfaces/TreeValueFunction.kt

@@ -1,8 +1,8 @@
-package org.nwapw.abacus.function
+package org.nwapw.abacus.function.interfaces
 
-import org.nwapw.abacus.function.applicable.ReducerApplicable
+import org.nwapw.abacus.function.Applicable
 import org.nwapw.abacus.number.NumberInterface
-import org.nwapw.abacus.tree.TreeNode
+import org.nwapw.abacus.tree.nodes.TreeNode
 
 /**
  * A function that operates on trees.
@@ -10,4 +10,4 @@ import org.nwapw.abacus.tree.TreeNode
  * A function that operates on parse tree nodes instead of on already simplified numbers.
  * Despite this, it returns a number, not a tree.
  */
-abstract class TreeValueFunction : ReducerApplicable<TreeNode, NumberInterface, NumberInterface>
+abstract class TreeValueFunction : Applicable<TreeNode, NumberInterface>

core/src/main/kotlin/org/nwapw/abacus/function/interfaces/TreeValueOperator.kt

@@ -1,8 +1,11 @@
-package org.nwapw.abacus.function
+package org.nwapw.abacus.function.interfaces
 
-import org.nwapw.abacus.function.applicable.ReducerApplicable
+import org.nwapw.abacus.function.Applicable
+import org.nwapw.abacus.function.Operator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
 import org.nwapw.abacus.number.NumberInterface
-import org.nwapw.abacus.tree.TreeNode
+import org.nwapw.abacus.tree.nodes.TreeNode
 
 /**
  * An operator that operates on trees.
@@ -15,4 +18,4 @@ import org.nwapw.abacus.tree.TreeNode
 abstract class TreeValueOperator(associativity: OperatorAssociativity, type: OperatorType,
                                  precedence: Int) :
         Operator(associativity, type, precedence),
-        ReducerApplicable<TreeNode, NumberInterface, NumberInterface>
+        Applicable<TreeNode, NumberInterface>

core/src/main/kotlin/org/nwapw/abacus/number/NumberInterface.kt

@@ -1,270 +1,276 @@
-package org.nwapw.abacus.number;
+package org.nwapw.abacus.number
-
+
-/**
+import org.nwapw.abacus.exception.ComputationInterruptedException
- * An interface used to represent a number.
+import org.nwapw.abacus.number.range.NumberRangeBuilder
- */
+
-public abstract class NumberInterface {
+abstract class NumberInterface: Comparable<NumberInterface> {
-
+
-    /**
+    /**
-     * Check if the thread was interrupted and
+     * Check if the thread was interrupted and
-     * throw an exception to end the computation.
+     * throw an exception to end the computation.
-     */
+     */
-    private static void checkInterrupted() {
+    private fun checkInterrupted(){
-        if (Thread.currentThread().isInterrupted())
+        if(Thread.currentThread().isInterrupted)
-            throw new ComputationInterruptedException();
+            throw ComputationInterruptedException()
-    }
+    }
-
+
-    /**
+    /**
-     * The maximum precision to which this number operates.
+     * Returns the integer representation of this number, discarding any fractional part,
-     *
+     * if int can hold the value.
-     * @return the precision.
+     *
-     */
+     * @return the integer value of this number.
-    public abstract int getMaxPrecision();
+     */
-
+    abstract fun intValue(): Int
-    /**
+    /**
-     * Multiplies this number by another, returning
+     * Same as Math.signum().
-     * a new number instance.
+     *
-     *
+     * @return 1 if this number is positive, -1 if this number is negative, 0 if this number is 0.
-     * @param multiplier the multiplier
+     */
-     * @return the result of the multiplication.
+    abstract fun signum(): Int
-     */
+
-    protected abstract NumberInterface multiplyInternal(NumberInterface multiplier);
+    /**
-
+     * The maximum precision to which this number operates.
-    /**
+     */
-     * Multiplies this number by another, returning
+    abstract val maxPrecision: Int
-     * a new number instance. Also, checks if the
+    /**
-     * thread has been interrupted, and if so, throws
+     * Returns the smallest error this instance can tolerate depending
-     * an exception.
+     * on its precision and value.
-     *
+     */
-     * @param multiplier the multiplier
+    abstract val maxError: NumberInterface
-     * @return the result of the multiplication.
+
-     */
+    /**
-    public final NumberInterface multiply(NumberInterface multiplier) {
+     * Adds this number to another, returning
-        checkInterrupted();
+     * a new number instance.
-        return multiplyInternal(multiplier);
+     *
-    }
+     * @param summand the summand
-
+     * @return the result of the summation.
-    /**
+     */
-     * Divides this number by another, returning
+    abstract fun addInternal(summand: NumberInterface): NumberInterface
-     * a new number instance.
+    /**
-     *
+     * Subtracts another number from this number,
-     * @param divisor the divisor
+     * a new number instance.
-     * @return the result of the division.
+     *
-     */
+     * @param subtrahend the subtrahend.
-    protected abstract NumberInterface divideInternal(NumberInterface divisor);
+     * @return the result of the subtraction.
-
+     */
-    /**
+    abstract fun subtractInternal(subtrahend: NumberInterface): NumberInterface
-     * Divides this number by another, returning
+    /**
-     * a new number instance. Also, checks if the
+     * Multiplies this number by another, returning
-     * thread has been interrupted, and if so, throws
+     * a new number instance.
-     * an exception.
+     *
-     *
+     * @param multiplier the multiplier
-     * @param divisor the divisor
+     * @return the result of the multiplication.
-     * @return the result of the division.
+     */
-     */
+    abstract fun multiplyInternal(multiplier: NumberInterface): NumberInterface
-    public final NumberInterface divide(NumberInterface divisor) {
+    /**
-        checkInterrupted();
+     * Divides this number by another, returning
-        return divideInternal(divisor);
+     * a new number instance.
-    }
+     *
-
+     * @param divisor the divisor
-    /**
+     * @return the result of the division.
-     * Adds this number to another, returning
+     */
-     * a new number instance.
+    abstract fun divideInternal(divisor: NumberInterface): NumberInterface
-     *
+    /**
-     * @param summand the summand
+     * Returns a new instance of this number with
-     * @return the result of the summation.
+     * the sign flipped.
-     */
+     *
-    protected abstract NumberInterface addInternal(NumberInterface summand);
+     * @return the new instance.
-
+     */
-    /**
+    abstract fun negateInternal(): NumberInterface
-     * Adds this number to another, returning
+    /**
-     * a new number instance. Also, checks if the
+     * Raises this number to an integer power.
-     * thread has been interrupted, and if so, throws
+     *
-     * an exception.
+     * @param exponent the exponent to which to take the number.
-     *
+     * @return the resulting value.
-     * @param summand the summand
+     */
-     * @return the result of the summation.
+    abstract fun intPowInternal(pow: Int): NumberInterface
-     */
+    /**
-    public final NumberInterface add(NumberInterface summand) {
+     * Returns the least integer greater than or equal to the number.
-        checkInterrupted();
+     *
-        return addInternal(summand);
+     * @return the least integer greater or equal to the number, if int can hold the value.
-    }
+     */
-
+    abstract fun ceilingInternal(): NumberInterface
-    /**
+    /**
-     * Subtracts another number from this number,
+     * Return the greatest integer less than or equal to the number.
-     * a new number instance.
+     *
-     *
+     * @return the greatest integer smaller or equal the number.
-     * @param subtrahend the subtrahend.
+     */
-     * @return the result of the subtraction.
+    abstract fun floorInternal(): NumberInterface
-     */
+    /**
-    protected abstract NumberInterface subtractInternal(NumberInterface subtrahend);
+     * Returns the fractional part of the number.
-
+     *
-    /**
+     * @return the fractional part of the number.
-     * Subtracts another number from this number,
+     */
-     * a new number instance. Also, checks if the
+    abstract fun fractionalPartInternal(): NumberInterface
-     * thread has been interrupted, and if so, throws
+
-     * an exception.
+    /**
-     *
+     * Adds this number to another, returning
-     * @param subtrahend the subtrahend.
+     * a new number instance. Also, checks if the
-     * @return the result of the subtraction.
+     * thread has been interrupted, and if so, throws
-     */
+     * an exception.
-    public final NumberInterface subtract(NumberInterface subtrahend) {
+     *
-        checkInterrupted();
+     * @param summand the summand
-        return subtractInternal(subtrahend);
+     * @return the result of the summation.
-    }
+     */
-
+    fun add(summand: NumberInterface): NumberInterface {
-    /**
+        checkInterrupted()
-     * Returns a new instance of this number with
+        return addInternal(summand)
-     * the sign flipped.
+    }
-     *
+
-     * @return the new instance.
+    /**
-     */
+     * Subtracts another number from this number,
-    protected abstract NumberInterface negateInternal();
+     * a new number instance. Also, checks if the
-
+     * thread has been interrupted, and if so, throws
-
+     * an exception.
-    /**
+     *
-     * Returns a new instance of this number with
+     * @param subtrahend the subtrahend.
-     * the sign flipped. Also, checks if the
+     * @return the result of the subtraction.
-     * thread has been interrupted, and if so, throws
+     */
-     * an exception.
+    fun subtract(subtrahend: NumberInterface): NumberInterface {
-     *
+        checkInterrupted()
-     * @return the new instance.
+        return subtractInternal(subtrahend)
-     */
+    }
-    public final NumberInterface negate() {
+
-        checkInterrupted();
+    /**
-        return negateInternal();
+     * Multiplies this number by another, returning
-    }
+     * a new number instance. Also, checks if the
-
+     * thread has been interrupted, and if so, throws
-    /**
+     * an exception.
-     * Raises this number to an integer power.
+     *
-     *
+     * @param multiplier the multiplier
-     * @param exponent the exponent to which to take the number.
+     * @return the result of the multiplication.
-     * @return the resulting value.
+     */
-     */
+    fun multiply(multiplier: NumberInterface): NumberInterface {
-    protected abstract NumberInterface intPowInternal(int exponent);
+        checkInterrupted()
-
+        return multiplyInternal(multiplier)
-    /**
+    }
-     * Raises this number to an integer power. Also, checks if the
+
-     * thread has been interrupted, and if so, throws
+    /**
-     * an exception.
+     * Divides this number by another, returning
-     *
+     * a new number instance. Also, checks if the
-     * @param exponent the exponent to which to take the number.
+     * thread has been interrupted, and if so, throws
-     * @return the resulting value.
+     * an exception.
-     */
+     *
-    public final NumberInterface intPow(int exponent) {
+     * @param divisor the divisor
-        checkInterrupted();
+     * @return the result of the division.
-        return intPowInternal(exponent);
+     */
-    }
+    fun divide(divisor: NumberInterface): NumberInterface {
-
+        checkInterrupted()
-    /**
+        return divideInternal(divisor)
-     * Compares this number to another.
+    }
-     *
+
-     * @param number the number to compare to.
+    /**
-     * @return same as Integer.compare();
+     * Returns a new instance of this number with
-     */
+     * the sign flipped. Also, checks if the
-    public abstract int compareTo(NumberInterface number);
+     * thread has been interrupted, and if so, throws
-
+     * an exception.
-    /**
+     *
-     * Same as Math.signum().
+     * @return the new instance.
-     *
+     */
-     * @return 1 if this number is positive, -1 if this number is negative, 0 if this number is 0.
+    fun negate(): NumberInterface {
-     */
+        checkInterrupted()
-    public abstract int signum();
+        return negateInternal()
-
+    }
-    /**
+
-     * Returns the least integer greater than or equal to the number.
+    /**
-     *
+     * Raises this number to an integer power. Also, checks if the
-     * @return the least integer greater or equal to the number, if int can hold the value.
+     * thread has been interrupted, and if so, throws
-     */
+     * an exception.
-    protected abstract NumberInterface ceilingInternal();
+     *
-
+     * @param exponent the exponent to which to take the number.
-    /**
+     * @return the resulting value.
-     * Returns the least integer greater than or equal to the number.
+     */
-     * Also, checks if the thread has been interrupted, and if so, throws
+    fun intPow(exponent: Int): NumberInterface {
-     * an exception.
+        checkInterrupted()
-     *
+        return intPowInternal(exponent)
-     * @return the least integer bigger or equal to the number.
+    }
-     */
+
-    public final NumberInterface ceiling() {
+    /**
-        checkInterrupted();
+     * Returns the least integer greater than or equal to the number.
-        return ceilingInternal();
+     * Also, checks if the thread has been interrupted, and if so, throws
-    }
+     * an exception.
-
+     *
-    /**
+     * @return the least integer bigger or equal to the number.
-     * Return the greatest integer less than or equal to the number.
+     */
-     *
+    fun ceiling(): NumberInterface {
-     * @return the greatest integer smaller or equal the number.
+        checkInterrupted()
-     */
+        return ceilingInternal()
-    protected abstract NumberInterface floorInternal();
+    }
-
+
-    /**
+    /**
-     * Return the greatest integer less than or equal to the number.
+     * Return the greatest integer less than or equal to the number.
-     * Also, checks if the thread has been interrupted, and if so, throws
+     * Also, checks if the thread has been interrupted, and if so, throws
-     * an exception.
+     * an exception.
-     *
+     *
-     * @return the greatest int smaller than or equal to the number.
+     * @return the greatest int smaller than or equal to the number.
-     */
+     */
-    public final NumberInterface floor() {
+    fun floor(): NumberInterface {
-        checkInterrupted();
+        checkInterrupted()
-        return floorInternal();
+        return floorInternal()
-    }
+    }
-
+
-    /**
+    /**
-     * Returns the fractional part of the number.
+     * Returns the fractional part of the number, specifically x - floor(x).
-     *
+     * Also, checks if the thread has been interrupted,
-     * @return the fractional part of the number.
+     * and if so, throws an exception.
-     */
+     *
-    protected abstract NumberInterface fractionalPartInternal();
+     * @return the fractional part of the number.
-
+     */
-    /**
+    fun fractionalPart(): NumberInterface {
-     * Returns the fractional part of the number, specifically x - floor(x).
+        checkInterrupted()
-     * Also, checks if the thread has been interrupted,
+        return fractionalPartInternal()
-     * and if so, throws an exception.
+    }
-     *
+
-     * @return the fractional part of the number.
+    /**
-     */
+     * Checks whether the given number is an integer or not.
-    public final NumberInterface fractionalPart() {
+     *
-        checkInterrupted();
+     * @return whether the number is an integer or not.
-        return fractionalPartInternal();
+     */
-    }
+    fun isInteger() = fractionalPart().signum() == 0
-
+
-    /**
+    /**
-     * Returns the integer representation of this number, discarding any fractional part,
+     * Returns a NumberRangeBuilder object, which is used to create a range.
-     * if int can hold the value.
+     * The reason that this returns a builder and not an actual range is that
-     *
+     * the NumberRange needs to promote values passed to it, which
-     * @return the integer value of this number.
+     * requires an abacus instance.
-     */
+     * @param other the value at the bottom of the range.
-    public abstract int intValue();
+     * @return the resulting range builder.
-
+     */
-    /**
+    operator fun rangeTo(other: NumberInterface) = NumberRangeBuilder(this, other)
-     * Promotes this class to another number class.
+
-     *
+    /**
-     * @param toClass the class to promote to.
+     * Plus operator overloaded to allow "nice" looking math.
-     * @return the resulting new instance.
+     * @param other the value to add to this number.
-     */
+     * @return the result of the addition.
-    @Deprecated
+     */
-    protected abstract NumberInterface promoteToInternal(Class<? extends NumberInterface> toClass);
+    operator fun plus(other: NumberInterface) = add(other)
-
+    /**
-    /**
+     * Minus operator overloaded to allow "nice" looking math.
-     * Promotes this class to another number class. Also, checks if the
+     * @param other the value to subtract to this number.
-     * thread has been interrupted, and if so, throws
+     * @return the result of the subtraction.
-     * an exception.
+     */
-     *
+    operator fun minus(other: NumberInterface) = subtract(other)
-     * @param toClass the class to promote to.
+    /**
-     * @return the resulting new instance.
+     * Times operator overloaded to allow "nice" looking math.
-     */
+     * @param other the value to multiply this number by.
-    @Deprecated
+     * @return the result of the multiplication.
-    public final NumberInterface promoteTo(Class<? extends NumberInterface> toClass) {
+     */
-        checkInterrupted();
+    operator fun times(other: NumberInterface) = multiply(other)
-        return promoteToInternal(toClass);
+    /**
-    }
+     * Divide operator overloaded to allow "nice" looking math.
-
+     * @param other the value to divide this number by.
-    /**
+     * @return the result of the division.
-     * Returns the smallest error this instance can tolerate depending
+     */
-     * on its precision and value.
+    operator fun div(other: NumberInterface) = divide(other)
-     *
+    /**
-     * @return the smallest error that should be permitted in calculations.
+     * The plus operator.
-     */
+     * @return this number.
-    public abstract NumberInterface getMaxError();
+     */
-
+    operator fun unaryPlus() = this
-}
+    /**
+     * The minus operator.
+     * @return the negative of this number.
+     */
+    operator fun unaryMinus() = negate()
+
+}

core/src/main/kotlin/org/nwapw/abacus/number/promotion/NumberUtils.kt

@@ -0,0 +1,17 @@
+@file:JvmName("NumberUtils")
+package org.nwapw.abacus.number.promotion
+
+import org.nwapw.abacus.number.NumberInterface
+
+typealias PromotionPath = List<PromotionFunction>
+typealias NumberClass = Class<NumberInterface>
+
+/**
+ * Promote a number through this path. The functions in this path
+ * are applied in order to the number, and the final result is returned.
+ *
+ * @param from the number to start from.
+ */
+fun PromotionPath.promote(from: NumberInterface): NumberInterface {
+    return fold(from, { current, function -> function.promote(current) })
+}

core/src/main/kotlin/org/nwapw/abacus/number/promotion/PromotionFunction.kt

@@ -0,0 +1,20 @@
+package org.nwapw.abacus.number.promotion
+
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * Function that is used to promote a number from one type to another.
+ *
+ * A promotion function is used in the promotion system as a mean to
+ * actually "travel" down the promotion path.
+ */
+interface PromotionFunction {
+
+    /**
+     * Promotes the given [number] into another type.
+     * @param number the number to promote from.
+     * @return the new number with the same value.
+     */
+    fun promote(number: NumberInterface): NumberInterface
+
+}

core/src/main/kotlin/org/nwapw/abacus/number/promotion/PromotionManager.kt

@@ -0,0 +1,81 @@
+package org.nwapw.abacus.number.promotion
+
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.exception.PromotionException
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.NumberImplementation
+import org.nwapw.abacus.plugin.PluginListener
+import org.nwapw.abacus.plugin.PluginManager
+
+/**
+ * A class that handles promotions based on priority and the
+ * transition paths each implementation provides.
+ *
+ * @property abacus the Abacus instance to use to access other components.
+ */
+class PromotionManager(val abacus: Abacus) : PluginListener {
+
+    /**
+     * The already computed paths
+     */
+    val computePaths = mutableMapOf<Pair<NumberImplementation, NumberImplementation>, PromotionPath?>()
+
+    /**
+     * Computes a path between a starting and an ending implementation.
+     *
+     * @param from the implementation to start from.
+     * @param to the implementation to get to.
+     * @return the resulting promotion path, or null if it is not found
+     */
+    fun computePathBetween(from: NumberImplementation, to: NumberImplementation): PromotionPath? {
+        val fromName = abacus.pluginManager.interfaceImplementationNameFor(from.implementation)
+        val toName = abacus.pluginManager.interfaceImplementationNameFor(to.implementation)
+
+        if(fromName == toName) return listOf(object : PromotionFunction {
+            override fun promote(number: NumberInterface): NumberInterface {
+                return number
+            }
+        })
+
+        if(from.promotionPaths.containsKey(toName))
+            return listOf(from.promotionPaths[toName] ?: return null)
+        return null
+    }
+
+    /**
+     * Promote all the numbers in the list to the same number implementation, to ensure
+     * they can be used with each other. Finds the highest priority implementation
+     * in the list, and promotes all other numbers to it.
+     *
+     * @param numbers the numbers to promote.
+     * @return the resulting promotion result.
+     */
+    fun promote(vararg numbers: NumberInterface): PromotionResult {
+        val pluginManager = abacus.pluginManager
+        val implementations = numbers.map { pluginManager.interfaceImplementationFor(it.javaClass) }
+        val highestPriority = implementations.sortedBy { it.priority }.last()
+        return PromotionResult(items = numbers.map {
+            if (it.javaClass == highestPriority.implementation) it
+            else computePaths[pluginManager.interfaceImplementationFor(it.javaClass) to highestPriority]
+                    ?.promote(it) ?: throw PromotionException()
+        }.toTypedArray(), promotedTo = highestPriority)
+    }
+
+    override fun onLoad(manager: PluginManager) {
+        val implementations = manager.allNumberImplementations.map { manager.numberImplementationFor(it) }
+        for(first in implementations) {
+            for(second in implementations) {
+                val promoteFrom = if(second.priority > first.priority) first else second
+                val promoteTo = if(second.priority > first.priority) second else first
+                val path = computePathBetween(promoteFrom, promoteTo)
+                computePaths[promoteFrom to promoteTo] = path
+            }
+        }
+    }
+
+    override fun onUnload(manager: PluginManager) {
+        computePaths.clear()
+    }
+
+
+}

core/src/main/kotlin/org/nwapw/abacus/number/promotion/PromotionResult.kt

@@ -0,0 +1,12 @@
+package org.nwapw.abacus.number.promotion
+
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.NumberImplementation
+
+/**
+ * The result of promoting an array of NumberInterfaces.
+ *
+ * @param promotedTo the implementation to which the numbers were promoted.
+ * @param items the items the items resulting from the promotion.
+ */
+data class PromotionResult(val promotedTo: NumberImplementation, val items: Array<NumberInterface>)

core/src/main/kotlin/org/nwapw/abacus/number/range/NumberRange.kt

@@ -0,0 +1,29 @@
+package org.nwapw.abacus.number.range
+
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * A closed range designed specifically for [NumberInterface]
+ *
+ * Besides providing the usual functionality of a [ClosedRange], this range
+ * also handles promotion - that is, it's safe to use it with numbers of different
+ * implementations, even as starting and ending points.
+ *
+ * @property abacus the abacus instance used for promotion.
+ * @property start the starting point of the range.
+ * @property endInclusive the ending point of the range.
+ */
+class NumberRange(val abacus: Abacus,
+                  override val start: NumberInterface,
+                  override val endInclusive: NumberInterface): ClosedRange<NumberInterface> {
+
+    override operator fun contains(value: NumberInterface): Boolean {
+        val promotionResult = abacus.promotionManager.promote(start, endInclusive, value)
+        val newStart = promotionResult.items[0]
+        val newEnd = promotionResult.items[1]
+        val newValue = promotionResult.items[2]
+        return newValue >= newStart && newValue <= newEnd
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/number/range/NumberRangeBuilder.kt

@@ -0,0 +1,25 @@
+package org.nwapw.abacus.number.range
+
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * A utility class for creating [NumberRange] instances.
+ *
+ * Unlike a regular [ClosedRange], a NumberRange must have a third parameter,
+ * which is the [Abacus] instance that is used for promotion. However, the ".." operator
+ * is infix, and can only take two parameters. The solution is, instead of returning instances
+ * of NumberRange directly, to return a builder, which then provides a [with] infix function
+ * to attach it to an instance of Abacus.
+ * @property start the beginning of the range.
+ * @property endInclusive the end of the range.
+ */
+class NumberRangeBuilder(private val start: NumberInterface, private val endInclusive: NumberInterface) {
+
+    /**
+     * Generate a [NumberRange] with the given instance of [abacus].
+     * @return a new range with the given instance of Abacus.
+     */
+    infix fun with(abacus: Abacus) = NumberRange(abacus, start, endInclusive)
+
+}

core/src/main/kotlin/org/nwapw/abacus/parsing/Parser.kt

@@ -1,16 +1,17 @@
-package org.nwapw.abacus.parsing;
+package org.nwapw.abacus.parsing
 
-import org.nwapw.abacus.tree.TreeNode;
+import org.nwapw.abacus.tree.nodes.TreeNode
-
-import java.util.List;
 
 /**
- * An itnerface that provides the ability to convert a list of tokens
+ * Converter from tokens into a parse tree.
+ *
+ * An interface that provides the ability to convert a list of tokens
  * into a parse tree.
  *
  * @param <T> the type of tokens accepted by this parser.
  */
-public interface Parser<T> {
+
+interface Parser<in T> {
 
     /**
      * Constructs a tree out of the given tokens.
@@ -18,5 +19,6 @@ public interface Parser<T> {
      * @param tokens the tokens to construct a tree from.
      * @return the constructed tree, or null on error.
      */
-    public TreeNode constructTree(List<T> tokens);
+    fun constructTree(tokens: List<T>): TreeNode
-}
+
+}

core/src/main/kotlin/org/nwapw/abacus/parsing/Tokenizer.kt

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.parsing
+
+/**
+ * Converter from string to tokens.
+ *
+ * Interface that converts a string into a list
+ * of tokens of a certain type.
+ *
+ * @param <T> the type of the tokens produced.
+ */
+interface Tokenizer<out T> {
+
+    /**
+     * Converts a string into tokens.
+     *
+     * @param string the string to convert.
+     * @return the list of tokens, or null on error.
+     */
+    fun tokenizeString(string: String):  List<T>
+
+}

core/src/main/kotlin/org/nwapw/abacus/parsing/TreeBuilder.kt

@@ -0,0 +1,26 @@
+package org.nwapw.abacus.parsing
+
+import org.nwapw.abacus.tree.nodes.TreeNode
+
+/**
+ * Class to combine a [Tokenizer] and a [Parser]
+ *
+ * TreeBuilder class used to piece together a Tokenizer and
+ * Parser of the same kind. This is used to essentially avoid
+ * working with any parameters at all, and the generics
+ * in this class are used only to ensure the tokenizer and parser
+ * are of the same type.
+ *
+ * @param <T> the type of tokens created by the tokenizer and used by the parser.
+ */
+class TreeBuilder<T>(private val tokenizer: Tokenizer<T>, private val parser: Parser<T>) {
+
+    /**
+     * Parses the given [string] into a tree.
+     *
+     * @param string the string to parse into a tree.
+     * @return the resulting tree.
+     */
+    fun fromString(string: String): TreeNode = parser.constructTree(tokenizer.tokenizeString(string))
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorAdd.kt

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * The addition operator.
+ *
+ * This is a standard operator that simply performs addition.
+ */
+class OperatorAdd: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params[0] + params[1]
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorCaret.kt

@@ -0,0 +1,38 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.standard.StandardPlugin.*
+
+/**
+ * The power operator.
+ *
+ * This is a standard operator that brings one number to the power of the other.
+ */
+class OperatorCaret: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 2) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+                    && !(params[0].signum() == 0 && params[1].signum() == 0)
+                    && !(params[0].signum() == -1 && !params[1].isInteger())
+
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
+        val implementation = context.inheritedNumberImplementation
+        if (params[0].signum() == 0)
+            return implementation.instanceForString("0")
+        else if (params[1].signum() == 0)
+            return implementation.instanceForString("1")
+        //Detect integer bases:
+        if (params[0].isInteger()
+                && FUNCTION_ABS.apply(context, params[1]) < implementation.instanceForString(Integer.toString(Integer.MAX_VALUE))
+                && FUNCTION_ABS.apply(context, params[1]) >= implementation.instanceForString("1")) {
+            val newParams = arrayOf(params[0], params[1].fractionalPart())
+            return params[0].intPow(params[1].floor().intValue()) * applyInternal(context, newParams)
+        }
+        return FUNCTION_EXP.apply(context, FUNCTION_LN.apply(context, FUNCTION_ABS.apply(context, params[0])) * params[1])
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorDefine.kt

@@ -0,0 +1,28 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.TreeValueOperator
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.tree.nodes.TreeNode
+import org.nwapw.abacus.tree.nodes.VariableNode
+
+/**
+ * The definition operator.
+ *
+ * This is a standard operator that creates a definition - something that doesn't capture variable values
+ * when it's created, but rather the variables themselves, and changes when the variables it uses change.
+ */
+class OperatorDefine: TreeValueOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out TreeNode>) =
+            params.size == 2 && params[0] is VariableNode
+
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out TreeNode>): NumberInterface {
+        val assignTo = (params[0] as VariableNode).variable
+        context.setDefinition(assignTo, params[1])
+        return params[1].reduce(context.inheritedReducer)
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorDivide.kt

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * The division operator.
+ *
+ * This is a standard operator that simply performs division.
+ */
+class OperatorDivide: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params[0] / params[1]
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorFactorial.kt

@@ -0,0 +1,37 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * The factorial operator.
+ *
+ * This is a standard operator that simply evaluates the factorial of a number.
+ */
+class OperatorFactorial: NumberOperator(OperatorAssociativity.LEFT, OperatorType.UNARY_POSTFIX, 0) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+        params.size == 1
+                && params[0].isInteger()
+                && params[0].signum() >= 0
+
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
+        val implementation = context.inheritedNumberImplementation
+        val one = implementation.instanceForString("1")
+        if (params[0].signum() == 0) {
+            return one
+        }
+        var factorial = params[0]
+        var multiplier = params[0] - one
+        //It is necessary to later prevent calls of factorial on anything but non-negative integers.
+        while (multiplier.signum() == 1) {
+            factorial *= multiplier
+            multiplier -= one
+        }
+        return factorial
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorMultiply.kt

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * The multiplication operator.
+ *
+ * This is a standard operator that simply performs multiplication.
+ */
+class OperatorMultiply: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params[0] * params[1]
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorNcr.kt

@@ -0,0 +1,25 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.standard.StandardPlugin.*
+
+/**
+ * The "N choose R" operator.
+ *
+ * This is a standard operator that returns the number of possible combinations, regardless of order,
+ * of a certain size can be taken out of a pool of a bigger size.
+ */
+class OperatorNcr: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2 && params[0].isInteger()
+                    && params[1].isInteger()
+
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            OP_NPR.apply(context, *params) / OP_FACTORIAL.apply(context, params[1])
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorNegate.kt

@@ -0,0 +1,22 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * The negation operator.
+ *
+ * This is a standard operator that negates a number.
+ */
+class OperatorNegate: NumberOperator(OperatorAssociativity.LEFT, OperatorType.UNARY_PREFIX, 0) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 1
+
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            -params[0]
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorNpr.kt

@@ -0,0 +1,42 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * The "N pick R" operator.
+ *
+ * his is a standard operator that returns the number of possible combinations
+ * of a certain size can be taken out of a pool of a bigger size.
+ */
+class OperatorNpr: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2 && params[0].isInteger()
+                    && params[1].isInteger()
+
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
+        val implementation = context.inheritedNumberImplementation
+        if (params[0] < params[1] ||
+                params[0].signum() < 0 ||
+                params[0].signum() == 0 && params[1].signum() != 0)
+            return implementation.instanceForString("0")
+        var total = implementation.instanceForString("1")
+        var multiplyBy = params[0]
+        var remainingMultiplications = params[1]
+        val halfway = params[0] / implementation.instanceForString("2")
+        if (remainingMultiplications > halfway) {
+            remainingMultiplications = params[0] - remainingMultiplications
+        }
+        while (remainingMultiplications.signum() > 0) {
+            total *= multiplyBy
+            remainingMultiplications -= implementation.instanceForString("1")
+            multiplyBy -= implementation.instanceForString("1")
+        }
+        return total
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorSet.kt

@@ -0,0 +1,28 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.TreeValueOperator
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.tree.nodes.TreeNode
+import org.nwapw.abacus.tree.nodes.VariableNode
+
+/**
+ * The set operator.
+ *
+ * This is a standard operator that assigns a value to a variable name.
+ */
+class OperatorSet: TreeValueOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out TreeNode>) =
+            params.size == 2 && params[0] is VariableNode
+
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out TreeNode>): NumberInterface {
+        val assignTo = (params[0] as VariableNode).variable
+        val value = params[1].reduce(context.inheritedReducer)
+        context.setVariable(assignTo, value)
+        return value
+    }
+
+}

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorSubtract.kt

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * The subtraction operator.
+ *
+ * This is a standard operator that performs subtraction.
+ */
+class OperatorSubtract: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
+
+    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+            params[0] - params[1]
+
+}

core/src/main/kotlin/org/nwapw/abacus/tree/Reducer.kt

@@ -1,5 +1,7 @@
 package org.nwapw.abacus.tree
 
+import org.nwapw.abacus.tree.nodes.TreeNode
+
 /**
  * Reducer interface that takes a tree and returns a single value.
  *
@@ -14,6 +16,6 @@ interface Reducer<out T> {
      * @param treeNode the tree node to reduce.
      * @param children the list of children, of type T.
      */
-    fun reduceNode(treeNode: TreeNode, vararg children: Any): T?
+    fun reduceNode(treeNode: TreeNode, vararg children: Any): T
 
 }

core/src/main/kotlin/org/nwapw/abacus/tree/TreeNode.kt

@@ -1,10 +0,0 @@
-package org.nwapw.abacus.tree
-
-/**
- * A tree node.
- */
-abstract class TreeNode {
-
-    abstract fun <T : Any> reduce(reducer: Reducer<T>): T?
-
-}

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/BinaryNode.kt

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
 
 /**
  * A tree node that holds a binary operation.
@@ -11,10 +11,10 @@ package org.nwapw.abacus.tree
  * @param left the left node.
  * @param right the right node.
  */
-abstract class BinaryNode(val operation: String, val left: TreeNode? = null, val right: TreeNode?) : TreeNode() {
+abstract class BinaryNode(val operation: String, val left: TreeNode, val right: TreeNode) : TreeNode() {
 
     override fun toString(): String {
-        return "(" + (left?.toString() ?: "null") + operation + (right?.toString() ?: "null") + ")"
+        return "(" + left.toString() + operation + right.toString() + ")"
     }
 
 }

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/CallNode.kt

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
 
 /**
  * Represents a more generic function call.
@@ -7,13 +7,9 @@ package org.nwapw.abacus.tree
  * to extend this functionality.
  *
  * @param callTo the name of the things being called.
+ * @param children the children of this node.
  */
-abstract class CallNode(val callTo: String) : TreeNode() {
+abstract class CallNode(val callTo: String, val children: List<TreeNode>) : TreeNode() {
-
-    /**
-     * The list of children this node has.
-     */
-    val children: MutableList<TreeNode> = mutableListOf()
 
     override fun toString(): String {
         val buffer = StringBuffer()

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/NumberBinaryNode.kt

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
 
 /**
  * A binary operator node that reduces its children.
@@ -10,12 +12,12 @@ package org.nwapw.abacus.tree
  * @param left the left child of this node.
  * @param right the right child of this node.
  */
-class NumberBinaryNode(operation: String, left: TreeNode?, right: TreeNode?)
+class NumberBinaryNode(operation: String, left: TreeNode, right: TreeNode)
     : BinaryNode(operation, left, right) {
 
-    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
-        val left = left?.reduce(reducer) ?: return null
+        val left = left.reduce(reducer)
-        val right = right?.reduce(reducer) ?: return null
+        val right = right.reduce(reducer)
         return reducer.reduceNode(this, left, right)
     }
 

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/NumberFunctionNode.kt

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
 
 /**
  * A tree node that holds a function call.
@@ -8,10 +10,10 @@ package org.nwapw.abacus.tree
  *
  * @param function the function string.
  */
-class FunctionNode(function: String) : CallNode(function) {
+class NumberFunctionNode(function: String, children: List<TreeNode>) : CallNode(function, children) {
 
-    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
-        val children = Array<Any>(children.size, { children[it].reduce(reducer) ?: return null; })
+        val children = Array<Any>(children.size, { children[it].reduce(reducer) })
         return reducer.reduceNode(this, *children)
     }
 

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/NumberNode.kt

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
 
 /**
  * A tree node that holds a single number value.
@@ -10,7 +12,7 @@ package org.nwapw.abacus.tree
  */
 class NumberNode(val number: String) : TreeNode() {
 
-    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
         return reducer.reduceNode(this)
     }
 

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/NumberUnaryNode.kt

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
 
 /**
  * A unary operator node that reduces its children.
@@ -8,11 +10,11 @@ package org.nwapw.abacus.tree
  * @param operation the operation this node performs.
  * @param child the child this node should be applied to.
  */
-class NumberUnaryNode(operation: String, child: TreeNode?)
+class NumberUnaryNode(operation: String, child: TreeNode)
     : UnaryNode(operation, child) {
 
-    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
-        val child = applyTo?.reduce(reducer) ?: return null
+        val child = applyTo.reduce(reducer)
         return reducer.reduceNode(this, child)
     }
 

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/TreeNode.kt

@@ -0,0 +1,12 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A tree node.
+ */
+abstract class TreeNode {
+
+    abstract fun <T : Any> reduce(reducer: Reducer<T>): T
+
+}

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/TreeValueBinaryNode.kt

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
 
 /**
  * A tree node that represents a binary tree value operator.
@@ -11,10 +13,10 @@ package org.nwapw.abacus.tree
  * @param left the left child of this node.
  * @param right the right child of this node.
  */
-class TreeValueBinaryNode(operation: String, left: TreeNode?, right: TreeNode?)
+class TreeValueBinaryNode(operation: String, left: TreeNode, right: TreeNode)
     : BinaryNode(operation, left, right) {
 
-    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
         return reducer.reduceNode(this)
     }
 

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/TreeValueFunctionNode.kt

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
 
 /**
  * A tree node that represents a tree value function call.
@@ -7,9 +9,9 @@ package org.nwapw.abacus.tree
  * is mostly to help the reducer. Besides that, this class also does not
  * even attempt to reduce its children.
  */
-class TreeValueFunctionNode(name: String) : CallNode(name) {
+class TreeValueFunctionNode(name: String, children: List<TreeNode>) : CallNode(name, children) {
 
-    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
         return reducer.reduceNode(this)
     }
 

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/TreeValueUnaryNode.kt

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
 
 /**
  * A tree node that represents a unary tree value operator.
@@ -9,11 +11,11 @@ package org.nwapw.abacus.tree
  * @param operation the operation this node performs.
  * @param child the node the operation should be applied to.
  */
-class TreeValueUnaryNode(operation: String, child: TreeNode?)
+class TreeValueUnaryNode(operation: String, child: TreeNode)
     : UnaryNode(operation, child) {
 
-    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
-        return reducer.reduceNode(this);
+        return reducer.reduceNode(this)
     }
 
 }

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/UnaryNode.kt

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
 
 /**
  * A tree node that holds a unary operation.
@@ -9,10 +9,10 @@ package org.nwapw.abacus.tree
  * @param operation the operation applied to the given node.
  * @param applyTo the node to which the operation will be applied.
  */
-abstract class UnaryNode(val operation: String, val applyTo: TreeNode? = null) : TreeNode() {
+abstract class UnaryNode(val operation: String, val applyTo: TreeNode) : TreeNode() {
 
     override fun toString(): String {
-        return "(" + (applyTo?.toString() ?: "null") + ")" + operation
+        return "(" + applyTo.toString() + ")" + operation
     }
 
 }

core/src/main/kotlin/org/nwapw/abacus/tree/nodes/VariableNode.kt

@@ -1,4 +1,6 @@
-package org.nwapw.abacus.tree
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
 
 /**
  * A tree node that holds a placeholder variable.
@@ -10,7 +12,7 @@ package org.nwapw.abacus.tree
  */
 class VariableNode(val variable: String) : TreeNode() {
 
-    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
         return reducer.reduceNode(this)
     }
 

core/src/main/kotlin/org/nwapw/abacus/tree/standard/NumberReducer.kt

@@ -0,0 +1,67 @@
+package org.nwapw.abacus.tree.standard
+
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.context.EvaluationContext
+import org.nwapw.abacus.exception.NumberReducerException
+import org.nwapw.abacus.exception.ReductionException
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.tree.Reducer
+import org.nwapw.abacus.tree.nodes.*
+
+class NumberReducer(val abacus: Abacus, context: EvaluationContext) : Reducer<NumberInterface> {
+
+    val context = context.mutableSubInstance()
+
+    init {
+        this.context.reducer = this
+    }
+
+    override fun reduceNode(treeNode: TreeNode, vararg children: Any): NumberInterface {
+        val promotionManager = abacus.promotionManager
+        return when(treeNode){
+            is NumberNode -> {
+                context.inheritedNumberImplementation.instanceForString(treeNode.number)
+            }
+            is VariableNode -> {
+                val variable = context.getVariable(treeNode.variable)
+                if(variable != null) return variable
+                val definition = context.getDefinition(treeNode.variable)
+                if(definition != null) return definition.reduce(this)
+                throw NumberReducerException("variable is not defined.")
+            }
+            is NumberUnaryNode -> {
+                val child = children[0] as NumberInterface
+                context.numberImplementation = abacus.pluginManager.interfaceImplementationFor(child.javaClass)
+                abacus.pluginManager.operatorFor(treeNode.operation)
+                        .apply(context, child)
+            }
+            is NumberBinaryNode -> {
+                val left = children[0] as NumberInterface
+                val right = children[1] as NumberInterface
+                val promotionResult = promotionManager.promote(left, right)
+                context.numberImplementation = promotionResult.promotedTo
+                abacus.pluginManager.operatorFor(treeNode.operation).apply(context, *promotionResult.items)
+            }
+            is NumberFunctionNode -> {
+                val promotionResult = promotionManager
+                        .promote(*children.map { it as NumberInterface }.toTypedArray())
+                context.numberImplementation = promotionResult.promotedTo
+                abacus.pluginManager.functionFor(treeNode.callTo).apply(context, *promotionResult.items)
+            }
+            is TreeValueUnaryNode -> {
+                abacus.pluginManager.treeValueOperatorFor(treeNode.operation)
+                        .apply(context, treeNode.applyTo)
+            }
+            is TreeValueBinaryNode -> {
+                abacus.pluginManager.treeValueOperatorFor(treeNode.operation)
+                        .apply(context, treeNode.left, treeNode.right)
+            }
+            is TreeValueFunctionNode -> {
+                abacus.pluginManager.treeValueFunctionFor(treeNode.callTo)
+                        .apply(context, *treeNode.children.toTypedArray())
+            }
+            else -> throw ReductionException("unrecognized tree node.")
+        }
+    }
+
+}

core/src/test/java/org/nwapw/abacus/tests/CalculationTests.java

@@ -5,34 +5,36 @@ import org.junit.BeforeClass;
 import org.junit.Test;
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.config.Configuration;
+import org.nwapw.abacus.exception.DomainException;
 import org.nwapw.abacus.number.NumberInterface;
-import org.nwapw.abacus.plugin.StandardPlugin;
+import org.nwapw.abacus.plugin.standard.StandardPlugin;
-import org.nwapw.abacus.tree.TreeNode;
+import org.nwapw.abacus.tree.nodes.TreeNode;
 
 public class CalculationTests {
 
-    private static Abacus abacus = new Abacus(new Configuration(0, "precise", new String[]{}));
+    private static Abacus abacus = new Abacus(new Configuration( "precise", new String[]{}));
 
     @BeforeClass
     public static void prepareTests() {
         abacus.getPluginManager().addInstantiated(new StandardPlugin(abacus.getPluginManager()));
-        abacus.getPluginManager().load();
+        abacus.reload();
     }
 
     private void testOutput(String input, String parseOutput, String output) {
         TreeNode parsedTree = abacus.parseString(input);
-        Assert.assertNotNull(parsedTree);
         Assert.assertEquals(parsedTree.toString(), parseOutput);
-        NumberInterface result = abacus.evaluateTree(parsedTree);
+        NumberInterface result = abacus.evaluateTree(parsedTree).getValue();
         Assert.assertNotNull(result);
         Assert.assertTrue(result.toString().startsWith(output));
     }
 
-    private void testEvalError(String input, String parseOutput) {
+    private void testDomainException(String input, String parseOutput) {
         TreeNode parsedTree = abacus.parseString(input);
-        Assert.assertNotNull(parsedTree);
         Assert.assertEquals(parsedTree.toString(), parseOutput);
-        Assert.assertNull(abacus.evaluateTree(parsedTree));
+        try {
+            abacus.evaluateTree(parsedTree);
+            Assert.fail("Function did not throw DomainException.");
+        } catch (DomainException e){ }
     }
 
     @Test
@@ -73,7 +75,7 @@ public class CalculationTests {
 
     @Test
     public void testLn() {
-        testEvalError("ln(-1)", "ln((1)`)");
+        testDomainException("ln(-1)", "ln((1)`)");
         testOutput("ln2", "ln(2)", "0.6931471805599453094172321214581765680755");
     }
 
@@ -100,8 +102,8 @@ public class CalculationTests {
         testOutput("2^-1", "(2^(1)`)", "0.5");
         testOutput("2^50", "(2^50)", "112589990684262");
         testOutput("7^(-sqrt2*17)", "(7^((sqrt(2)*17))`)", "4.81354609155297814551845300063563");
-        testEvalError("0^0", "(0^0)");
+        testDomainException("0^0", "(0^0)");
-        testEvalError("(-13)^.9999", "((13)`^.9999)");
+        testDomainException("(-13)^.9999", "((13)`^.9999)");
     }
 
 }

core/src/test/java/org/nwapw/abacus/tests/LexerTests.java

@@ -3,7 +3,7 @@ package org.nwapw.abacus.tests;
 import org.junit.Assert;
 import org.junit.Test;
 import org.nwapw.abacus.lexing.Lexer;
-import org.nwapw.abacus.lexing.pattern.Match;
+import org.nwapw.abacus.lexing.Match;
 
 import java.util.List;
 

core/src/test/java/org/nwapw/abacus/tests/RangeTests.java

@@ -0,0 +1,95 @@
+package org.nwapw.abacus.tests;
+
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.nwapw.abacus.Abacus;
+import org.nwapw.abacus.config.Configuration;
+import org.nwapw.abacus.number.promotion.PromotionFunction;
+import org.nwapw.abacus.number.standard.NaiveNumber;
+import org.nwapw.abacus.number.range.NumberRange;
+import org.nwapw.abacus.number.standard.PreciseNumber;
+import org.nwapw.abacus.plugin.standard.StandardPlugin;
+
+public class RangeTests {
+
+    private static Abacus abacus = new Abacus(new Configuration( "precise", new String[]{}));
+    private static PromotionFunction naivePromotion = i -> new NaiveNumber((i.toString()));
+    private static PromotionFunction precisePromotion = i -> new PreciseNumber((i.toString()));
+
+    @BeforeClass
+    public static void prepareTests() {
+        abacus.getPluginManager().addInstantiated(new StandardPlugin(abacus.getPluginManager()));
+        abacus.reload();
+    }
+
+    public static NumberRange naiveRange(String bottom, String top) {
+        return new NaiveNumber(bottom).rangeTo(new NaiveNumber(top)).with(abacus);
+    }
+
+    @Test
+    public void testNaiveRange(){
+        NumberRange range = naiveRange("0", "10");
+        Assert.assertTrue(range.getStart().toString().startsWith("0"));
+        Assert.assertTrue(range.getEndInclusive().toString().startsWith("10"));
+    }
+
+    @Test
+    public void testNaiveRangeBelow() {
+        NumberRange range = naiveRange("0", "10");
+        Assert.assertFalse(range.contains(new NaiveNumber("-10")));
+    }
+
+    @Test
+    public void testNaiveRangeAbove() {
+        NumberRange range = naiveRange("0", "10");
+        Assert.assertFalse(range.contains(new NaiveNumber("20")));
+    }
+
+    @Test
+    public void testNaiveRangeJustWithinBottom() {
+        NumberRange range = naiveRange("0", "10");
+        Assert.assertTrue(range.contains(new NaiveNumber("0")));
+    }
+
+    @Test
+    public void testNaiveRangeJustWithinTop() {
+        NumberRange range = naiveRange("0", "10");
+        Assert.assertTrue(range.contains(new NaiveNumber("10")));
+    }
+
+    @Test
+    public void testNaiveRangeWithin() {
+        NumberRange range = naiveRange("0", "10");
+        Assert.assertTrue(range.contains(new NaiveNumber("5")));
+    }
+
+    public static void addTestPromotionPaths() {
+        StandardPlugin.IMPLEMENTATION_NAIVE.getPromotionPaths().put("precise", precisePromotion);
+        StandardPlugin.IMPLEMENTATION_PRECISE.getPromotionPaths().put("naive", naivePromotion);
+        abacus.reload();
+    }
+
+    public static void removeTestPromotionPaths() {
+        StandardPlugin.IMPLEMENTATION_NAIVE.getPromotionPaths().remove("precise");
+        StandardPlugin.IMPLEMENTATION_NAIVE.getPromotionPaths().remove("naive");
+        abacus.reload();
+    }
+
+    @Test
+    public void testPromotionWithin() {
+        addTestPromotionPaths();
+        NumberRange range = naiveRange("0", "10");
+        Assert.assertTrue(range.contains(new PreciseNumber("5")));
+        removeTestPromotionPaths();
+    }
+
+    @Test
+    public void testPromotionOutside(){
+        addTestPromotionPaths();
+        NumberRange range = naiveRange("0","10");
+        Assert.assertFalse(range.contains(new PreciseNumber("20")));
+        removeTestPromotionPaths();
+    }
+
+}

core/src/test/java/org/nwapw/abacus/tests/TokenizerTests.java

@@ -5,27 +5,30 @@ import org.junit.BeforeClass;
 import org.junit.Test;
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.config.Configuration;
+import org.nwapw.abacus.context.MutableEvaluationContext;
 import org.nwapw.abacus.function.*;
-import org.nwapw.abacus.lexing.pattern.Match;
+import org.nwapw.abacus.function.interfaces.NumberFunction;
+import org.nwapw.abacus.function.interfaces.NumberOperator;
+import org.nwapw.abacus.lexing.Match;
 import org.nwapw.abacus.number.NumberInterface;
-import org.nwapw.abacus.parsing.LexerTokenizer;
+import org.nwapw.abacus.parsing.standard.LexerTokenizer;
 import org.nwapw.abacus.plugin.Plugin;
-import org.nwapw.abacus.tree.TokenType;
+import org.nwapw.abacus.parsing.standard.TokenType;
 
 import java.util.List;
 
 public class TokenizerTests {
 
-    private static Abacus abacus = new Abacus(new Configuration(0, "precise", new String[]{}));
+    private static Abacus abacus = new Abacus(new Configuration("precise", new String[]{}));
     private static LexerTokenizer lexerTokenizer = new LexerTokenizer();
     private static NumberFunction subtractFunction = new NumberFunction() {
         @Override
-        public boolean matchesParams(NumberInterface[] params) {
+        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
             return params.length == 2;
         }
 
         @Override
-        public NumberInterface applyInternal(NumberInterface[] params) {
+        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
             return params[0].subtract(params[1]);
         }
     };
@@ -36,26 +39,26 @@ public class TokenizerTests {
                     0) {
 
                 @Override
-                public boolean matchesParams(NumberInterface[] params) {
+                public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
                     return true;
                 }
 
-                @Override
+                                @Override
-                public NumberInterface applyInternal(NumberInterface[] params) {
+                public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
-                    return subtractFunction.apply(params);
+                    return subtractFunction.apply(context, params);
                 }
             });
             registerOperator("-", new NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX,
                     0) {
 
                 @Override
-                public boolean matchesParams(NumberInterface[] params) {
+                public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
                     return true;
                 }
 
-                @Override
+                                @Override
-                public NumberInterface applyInternal(NumberInterface[] params) {
+                public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
-                    return subtractFunction.apply(params);
+                    return subtractFunction.apply(context, params);
                 }
             });
             registerFunction("subtract", subtractFunction);
@@ -79,7 +82,7 @@ public class TokenizerTests {
     public static void prepareTests() {
         abacus.getPluginManager().addListener(lexerTokenizer);
         abacus.getPluginManager().addInstantiated(testPlugin);
-        abacus.getPluginManager().load();
+        abacus.reload();
     }
 
     @Test

docs/_layouts/home.html

@@ -3,6 +3,7 @@
   {% include head.html %}
   <style>
   body {
+    margin: 0px;
     margin-top: 50px;
     color: white;
     text-align: center;
@@ -37,6 +38,58 @@
     background-color: #06e8a4;
     color: white;
   }
+
+  div.fullwidth {
+    width: 100%;
+    height: auto;
+    overflow: hidden;
+  }
+
+  div.fullwidth img {
+    max-width: 100%;
+    max-height: 450px;
+    margin: auto;
+    margin-top: 20px;
+    margin-bottom: 20px;
+    display: block;
+    border-radius: 5px;
+  }
+
+  div.white {
+    background-color: white;
+    color: black;
+  }
+
+  div.green {
+    background-color: #06e8a4;
+    color: white;
+  }
+
+  div.fullwidth div.double {
+    height: 100%;
+    text-align: left;
+    width: 50%;
+    box-sizing: border-box;
+    padding: 40px;
+    float: left;
+    background-color: inherit;
+  }
+
+  @media (max-width: 750px) {
+    div.fullwidth div.double {
+      width: 100%;
+      padding: 15px;
+    }
+    div.fullwidth img {
+      margin-top: 0px;
+      margin-bottom: 0px;
+    }
+  }
+
+  div.fullwidth div.double h1, h2, h3, h4, h5, h6 {
+    text-align: center;
+  }
+
   </style>
   <body>
   <img src="https://raw.githubusercontent.com/DanilaFe/abacus/master/image/logo.png" id="logo">
@@ -49,5 +102,58 @@
     <a class="button inverted" href="https://github.com/DanilaFe/abacus/wiki">Wiki</a>
   </div>
   <img src="http://i.imgur.com/Min70QY.png" title="source: imgur.com" id="image_preview"/>
+  <h2>Features</h2>
+  <div class="fullwidth white">
+    <div class="double">
+      <img src="https://i.imgur.com/gmGJBBK.png">
+    </div>
+    <div class="double">
+      <h2>Precision</h2>
+      Abacus uses a mathematical tool called Taylor Series to determine values
+      as accurate as the user desires. Of course, this comes with some
+      performance issues with larger numbers. However, Abacus has been
+      tested to generate the value of e correctly to a thousand digits.
+    </div>
+  </div>
+  <div class="fullwidth green">
+    <div class="double">
+      <h2>Configurable and Customizable</h2>
+      The very first idea for Abacus was inspired by how difficult it was
+      to program a TI-84 calculator. Only two languages were available, TI-BASIC
+      and Assembly, the latter having virtually no documentation. Determined
+      to be better than a TI-84, Abacus implemented a plugin system that allows
+      users to easily create and add plugins written in the same programming
+      language as Abacus itself - Java. These plugins can access the full
+      power of the language, and implement their own ways of handling numbers,
+      as well as their own functions and even operators.<br><br>
+      Besides the ability to add plugins, Abacus also adds some general
+      options that can be used to make the user's experience more pleasant.
+      For instance, it allows for a computation limit to be set in order
+      to prevent excessively long evaluation: 8!!! is, for example, an expression
+      that even Wolfram Alpha doesn't compute accurately, and will never finish
+      on Abacus (it's simply too large). The computation limit will allow Abacus
+      to kill a computation if it takes too long. Support for user-definable
+      precision is also planned.
+    </div>
+    <div class="double">
+      <img src="https://i.imgur.com/JzenWPV.png">
+    </div>
+  </div>
+  <div class="fullwidth white">
+    <div class="double">
+      <img src="https://i.imgur.com/jY17I3A.png">
+    </div>
+    <div class="double">
+      <h2>Built-in Documentation</h2>
+      Abacus plugins are given a mechanism to register documentation for
+      the functions that they provide. The Abacus GUI displays these
+      functions in a searchable list, allowing the user to read the parameters
+      that have to be supplied to each function, as well as learn about
+      its return value.<br><br>
+      The search finds functions not only by their names, but also by relevant
+      terms mentioned in the function's description, thus allowing related
+      functions to be displayed together.
+    </div>
+  </div>
   </body>
 </html>

docs/assets/css/main.scss

@@ -7,7 +7,7 @@ $code-color: #efefef;
 $accent-color: #00AFE8;
 $clear-color: white;
 $title-font: "Open Sans";
-$text-font: Helvetica;
+$text-font: "Raleway";
 $code-font: "Source Code Pro";
 $max-width: 850px;
 

fx/build.gradle

@@ -1,6 +1,7 @@
 apply plugin: 'application'
 
 dependencies {
+    compile 'com.moandjiezana.toml:toml4j:0.7.1'
     compile project(':core')
 }
 

fx/src/main/java/org/nwapw/abacus/fx/AbacusController.java

@@ -12,15 +12,15 @@ import javafx.util.Callback;
 import javafx.util.StringConverter;
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.config.Configuration;
+import org.nwapw.abacus.exception.AbacusException;
 import org.nwapw.abacus.function.Documentation;
 import org.nwapw.abacus.function.DocumentationType;
-import org.nwapw.abacus.number.ComputationInterruptedException;
+import org.nwapw.abacus.number.*;
-import org.nwapw.abacus.number.NumberInterface;
-import org.nwapw.abacus.plugin.ClassFinder;
 import org.nwapw.abacus.plugin.PluginListener;
 import org.nwapw.abacus.plugin.PluginManager;
-import org.nwapw.abacus.plugin.StandardPlugin;
+import org.nwapw.abacus.plugin.standard.StandardPlugin;
-import org.nwapw.abacus.tree.TreeNode;
+import org.nwapw.abacus.EvaluationResult;
+import org.nwapw.abacus.tree.nodes.TreeNode;
 
 import java.io.File;
 import java.io.IOException;
@@ -141,18 +141,14 @@ public class AbacusController implements PluginListener {
         private String attemptCalculation() {
             try {
                 TreeNode constructedTree = abacus.parseString(inputField.getText());
-                if (constructedTree == null) {
+                EvaluationResult result = abacus.evaluateTree(constructedTree);
-                    return ERR_SYNTAX;
+                NumberInterface evaluatedNumber = result.getValue();
-                }
-                NumberInterface evaluatedNumber = abacus.evaluateTree(constructedTree);
-                if (evaluatedNumber == null) {
-                    return ERR_EVAL;
-                }
                 String resultingString = evaluatedNumber.toString();
                 historyData.add(new HistoryModel(inputField.getText(), constructedTree.toString(), resultingString));
+                abacus.applyToContext(result.getResultingContext());
                 return resultingString;
-            } catch (ComputationInterruptedException exception) {
+            } catch (AbacusException exception) {
-                return ERR_STOP;
+                return exception.getMessage();
             } catch (RuntimeException exception) {
                 exception.printStackTrace();
                 return ERR_EXCEPTION;
@@ -195,7 +191,7 @@ public class AbacusController implements PluginListener {
      */
     private final Runnable TIMER_RUNNABLE = () -> {
         try {
-            Configuration abacusConfig = abacus.getConfiguration();
+            ExtendedConfiguration abacusConfig = (ExtendedConfiguration) abacus.getConfiguration();
             if (abacusConfig.getComputationDelay() == 0) return;
             Thread.sleep((long) (abacusConfig.getComputationDelay() * 1000));
             performStop();
@@ -255,12 +251,12 @@ public class AbacusController implements PluginListener {
             if (oldValue.equals(settingsTab)) alertIfApplyNeeded(true);
         });
 
-        abacus = new Abacus(new Configuration(CONFIG_FILE));
+        abacus = new Abacus(new ExtendedConfiguration(CONFIG_FILE));
         PluginManager abacusPluginManager = abacus.getPluginManager();
         abacusPluginManager.addListener(this);
         performScan();
 
-        computationLimitField.setText(Double.toString(abacus.getConfiguration().getComputationDelay()));
+        computationLimitField.setText(Double.toString(((ExtendedConfiguration) abacus.getConfiguration()).getComputationDelay()));
         computationLimitField.textProperty().addListener((observable, oldValue, newValue) -> {
             if (!newValue.matches("(\\d+(\\.\\d*)?)?")) {
                 computationLimitField.setText(oldValue);
@@ -318,13 +314,13 @@ public class AbacusController implements PluginListener {
         } catch (IOException | ClassNotFoundException e) {
             e.printStackTrace();
         }
-        abacusPluginManager.reload();
+        abacus.reload();
     }
 
     @FXML
     public void performReload() {
         alertIfApplyNeeded(true);
-        abacus.getPluginManager().reload();
+        abacus.reload();
     }
 
     @FXML
@@ -337,8 +333,8 @@ public class AbacusController implements PluginListener {
             if (!pluginEntry.isEnabled()) disabledPlugins.add(pluginEntry.getClassName());
         }
         if (computationLimitField.getText().matches("\\d*(\\.\\d+)?") && computationLimitField.getText().length() != 0)
-            configuration.setComputationDelay(Double.parseDouble(computationLimitField.getText()));
+            ((ExtendedConfiguration) configuration).setComputationDelay(Double.parseDouble(computationLimitField.getText()));
-        configuration.saveTo(CONFIG_FILE);
+        ((ExtendedConfiguration) configuration).saveTo(CONFIG_FILE);
         changesMade = false;
         reloadAlertShown = false;
     }
@@ -358,7 +354,12 @@ public class AbacusController implements PluginListener {
             enabledPlugins.add(plugin);
         }
         PluginManager pluginManager = abacus.getPluginManager();
-        functionList.addAll(manager.getAllFunctions().stream().map(name -> pluginManager.documentationFor(name, DocumentationType.FUNCTION))
+        functionList.addAll(manager.getAllFunctions().stream().map(name -> {
+            Documentation documentationInstance = pluginManager.documentationFor(name, DocumentationType.FUNCTION);
+            if(documentationInstance == null)
+                documentationInstance = new Documentation(name, "", "", "", DocumentationType.FUNCTION);
+            return documentationInstance;
+        })
                 .collect(Collectors.toCollection(ArrayList::new)));
         functionList.addAll(manager.getAllTreeValueFunctions().stream().map(name -> pluginManager.documentationFor(name, DocumentationType.TREE_VALUE_FUNCTION))
                 .collect(Collectors.toCollection(ArrayList::new)));

fx/src/main/java/org/nwapw/abacus/fx/ClassFinder.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.plugin;
+package org.nwapw.abacus.fx;
 
 import java.io.File;
 import java.io.IOException;

fx/src/main/kotlin/org/nwapw/abacus/fx/ExtendedConfiguration.kt

@@ -0,0 +1,72 @@
+package org.nwapw.abacus.fx
+
+import com.moandjiezana.toml.Toml
+import com.moandjiezana.toml.TomlWriter
+import org.nwapw.abacus.config.Configuration
+import java.io.File
+
+/**
+ * Additional settings for user interface.
+ *
+ * ExtendedConfiguration is used to add other settings
+ * that aren't built into Abacus core, but are necessary
+ * for the fx module.
+ *
+ * @property computationDelay the delay before which the computation stops.
+ * @param implementation the number implementation, same as [Configuration.numberImplementation]
+ * @param disabledPlugins the list of plugins that should be disabled, same as [Configuration.disabledPlugins]
+ */
+class ExtendedConfiguration(var computationDelay: Double = 0.0,
+                     implementation: String = "<default>",
+                     disabledPlugins: Array<String> = emptyArray())
+    : Configuration(implementation, disabledPlugins) {
+
+    companion object {
+        /**
+         * The default TOML.
+         */
+        val DEFAULT_TOML_STRING = """
+            computationDelay=0.0
+            implementation="naive"
+            disabledPlugins=[]
+            """
+        /**
+         * A reader with the default TOML data.
+         */
+        val DEFAULT_TOML_READER = Toml().read(DEFAULT_TOML_STRING)
+        /**
+         * A writer used to writing the configuration to disk.
+         */
+        val DEFAULT_TOML_WRITER = TomlWriter()
+    }
+
+    /**
+     * Constructs a new configuration from a file on disk.
+     * @param tomlFile the file from disk to load.
+     */
+    constructor(tomlFile: File) : this() {
+        val toml = Toml(DEFAULT_TOML_READER)
+        if(tomlFile.exists()) toml.read(tomlFile)
+        copyFrom(toml.to(ExtendedConfiguration::class.java))
+    }
+
+    /**
+     * Copies data from another configuration into this one.
+     * @param config the configuration to copy from.
+     */
+    fun copyFrom(config: ExtendedConfiguration) {
+        computationDelay = config.computationDelay
+        numberImplementation = config.numberImplementation
+        disabledPlugins.clear()
+        disabledPlugins.addAll(config.disabledPlugins)
+    }
+
+    /**
+     * Saves this configuration to a file.
+     * @param file the file to save to.
+     */
+    fun saveTo(file: File) {
+        DEFAULT_TOML_WRITER.write(this, file)
+    }
+
+}

fx/src/main/resources/abacus.fxml

@@ -54,7 +54,7 @@
                     <TextField fx:id="computationLimitField" GridPane.columnIndex="1" GridPane.rowIndex="2"/>
                     <FlowPane GridPane.columnIndex="0" GridPane.columnSpan="2" GridPane.rowIndex="3" hgap="10"
                               vgap="10">
-                        <Button text="Apply" onAction="#performSave"/>
+                        <Button text="Save" onAction="#performSave"/>
                         <Button text="Reload Plugins" onAction="#performReload"/>
                         <Button text="Apply and Reload" onAction="#performSaveAndReload"/>
                         <Button text="Scan Plugins" onAction="#performScan"/>