Merge pull request #56 from DanilaFe/version-update

Bump Gradle, Kotlin, and toml4j versions.

.gitignore

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

build.gradle

@@ -1,15 +1,29 @@
+buildscript {
+    ext.kotlin_version = '1.2.40'
+    ext.dokka_version = '0.9.16'
+
+    repositories {
+        jcenter()
+    }
+
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+        classpath "org.jetbrains.dokka:dokka-gradle-plugin:$dokka_version"
+    }
+}
+
+subprojects {
+
     apply plugin: 'java'
-apply plugin: 'application'
+    apply plugin: 'kotlin'
+    apply plugin: 'org.jetbrains.dokka'
 
     repositories {
         mavenCentral()
     }
 
     dependencies {
-    compile 'com.moandjiezana.toml:toml4j:0.7.1'
-    testCompile 'junit:junit:4.12'
+        compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:1.2.40"
+    }
 }
 
-// Define the main class for the application
-mainClassName = 'org.nwapw.abacus.Abacus'
-

core/build.gradle

@@ -0,0 +1,3 @@
+dependencies {
+    testCompile 'junit:junit:4.12'
+}

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

@@ -0,0 +1,16 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * Exception thrown when the computation is interrupted by
+ * the user.
+ */
+public class ComputationInterruptedException extends AbacusException {
+
+    /**
+     * Creates a new exception of this type.
+     */
+    public ComputationInterruptedException() {
+        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/function/DocumentationType.java

@@ -0,0 +1,11 @@
+package org.nwapw.abacus.function;
+
+/**
+ * Enum that holds the type of documentation that has been
+ * registered with Abacus.
+ */
+public enum DocumentationType {
+
+    FUNCTION, TREE_VALUE_FUNCTION
+
+}

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.Match;
 import org.nwapw.abacus.lexing.pattern.Pattern;
-import org.nwapw.abacus.lexing.pattern.PatternNode;
+import org.nwapw.abacus.lexing.pattern.nodes.EndNode;
+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 =
-            new HashMap<Character, Function<PatternChain<T>, PatternChain<T>>>() {{
+    private Map<Character, Transformation<T>> operations =
+            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.outputStates.add(newTail);
-        chain.tail.outputStates.add(newTail);
-        newTail.outputStates.add(newHead);
+        newHead.getOutputStates().add(chain.head);
+        newHead.getOutputStates().add(newTail);
+        chain.tail.getOutputStates().add(newTail);
+        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.outputStates.add(newTail);
-        chain.tail.outputStates.add(newTail);
+        newHead.getOutputStates().add(chain.head);
+        newHead.getOutputStates().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);
-            chain.tail.outputStates.add(tail);
+            head.getOutputStates().add(chain.head);
+            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.
@@ -15,7 +15,7 @@ public class ValueNode<T> extends PatternNode<T> {
     /**
      * Creates a new node that matches the given character.
      *
-     * @param value
+     * @param value the character value of the node.
      */
     public ValueNode(char value) {
         this.value = value;

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

@@ -1,9 +1,11 @@
-package org.nwapw.abacus.number;
+package org.nwapw.abacus.number.standard;
+
+import org.nwapw.abacus.number.NumberInterface;
 
 /**
  * An implementation of NumberInterface using a double.
  */
-public class NaiveNumber implements NumberInterface {
+public class NaiveNumber extends NumberInterface {
 
     /**
      * The number zero.
@@ -26,6 +28,7 @@ public class NaiveNumber implements NumberInterface {
     public NaiveNumber(String value) {
         this(Double.parseDouble(value));
     }
+
     /**
      * Creates a new NaiveNumber with the given value.
      *
@@ -41,32 +44,32 @@ public class NaiveNumber implements NumberInterface {
     }
 
     @Override
-    public NumberInterface multiply(NumberInterface multiplier) {
+    public NumberInterface multiplyInternal(NumberInterface multiplier) {
         return new NaiveNumber(value * ((NaiveNumber) multiplier).value);
     }
 
     @Override
-    public NumberInterface divide(NumberInterface divisor) {
+    public NumberInterface divideInternal(NumberInterface divisor) {
         return new NaiveNumber(value / ((NaiveNumber) divisor).value);
     }
 
     @Override
-    public NumberInterface add(NumberInterface summand) {
+    public NumberInterface addInternal(NumberInterface summand) {
         return new NaiveNumber(value + ((NaiveNumber) summand).value);
     }
 
     @Override
-    public NumberInterface subtract(NumberInterface subtrahend) {
+    public NumberInterface subtractInternal(NumberInterface subtrahend) {
         return new NaiveNumber(value - ((NaiveNumber) subtrahend).value);
     }
 
     @Override
-    public NumberInterface negate() {
+    public NumberInterface negateInternal() {
         return new NaiveNumber(-value);
     }
 
     @Override
-    public NumberInterface intPow(int exponent) {
+    public NumberInterface intPowInternal(int exponent) {
         if (exponent == 0) {
             return NaiveNumber.ONE;
         }
@@ -94,17 +97,17 @@ public class NaiveNumber implements NumberInterface {
     }
 
     @Override
-    public NumberInterface ceiling() {
+    public NumberInterface ceilingInternal() {
         return new NaiveNumber(Math.ceil(value));
     }
 
     @Override
-    public NumberInterface floor() {
+    public NumberInterface floorInternal() {
         return new NaiveNumber(Math.floor(value));
     }
 
     @Override
-    public NumberInterface fractionalPart() {
+    public NumberInterface fractionalPartInternal() {
         return new NaiveNumber(value - Math.floor(value));
     }
 
@@ -113,19 +116,14 @@ public class NaiveNumber implements NumberInterface {
         return (int) value;
     }
 
-    @Override
-    public NumberInterface promoteTo(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);
     }
 
+    @Override
+    public NumberInterface getMaxError() {
+        return new NaiveNumber(Math.pow(10, -18));
+    }
 }
 

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

@@ -1,13 +1,15 @@
-package org.nwapw.abacus.number;
+package org.nwapw.abacus.number.standard;
+
+import org.nwapw.abacus.number.NumberInterface;
 
 import java.math.BigDecimal;
-import java.math.RoundingMode;
+import java.math.MathContext;
 
 /**
  * A number that uses a BigDecimal to store its value,
  * leading to infinite possible precision.
  */
-public class PreciseNumber implements NumberInterface {
+public class PreciseNumber extends NumberInterface {
 
     /**
      * The number one.
@@ -22,6 +24,21 @@ public class PreciseNumber implements NumberInterface {
      */
     public static final PreciseNumber TEN = new PreciseNumber(BigDecimal.TEN);
 
+    /**
+     * The number of extra significant figures kept in calculations before rounding for output.
+     */
+    private static int numExtraInternalSigFigs = 15;
+
+    /**
+     * MathContext that is used when rounding a number prior to output.
+     */
+    private static MathContext outputContext = new MathContext(50);
+
+    /**
+     * MathContext that is actually used in calculations.
+     */
+    private static MathContext internalContext = new MathContext(outputContext.getPrecision() + numExtraInternalSigFigs);
+
     /**
      * The value of the PreciseNumber.
      */
@@ -48,31 +65,31 @@ public class PreciseNumber implements NumberInterface {
 
     @Override
     public int getMaxPrecision() {
-        return 65;
+        return internalContext.getPrecision();
     }
 
     @Override
-    public NumberInterface multiply(NumberInterface multiplier) {
+    public NumberInterface multiplyInternal(NumberInterface multiplier) {
         return new PreciseNumber(this.value.multiply(((PreciseNumber) multiplier).value));
     }
 
     @Override
-    public NumberInterface divide(NumberInterface divisor) {
-        return new PreciseNumber(value.divide(((PreciseNumber) divisor).value, this.getMaxPrecision(), RoundingMode.HALF_UP));
+    public NumberInterface divideInternal(NumberInterface divisor) {
+        return new PreciseNumber(value.divide(((PreciseNumber) divisor).value, internalContext));
     }
 
     @Override
-    public NumberInterface add(NumberInterface summand) {
+    public NumberInterface addInternal(NumberInterface summand) {
         return new PreciseNumber(value.add(((PreciseNumber) summand).value));
     }
 
     @Override
-    public NumberInterface subtract(NumberInterface subtrahend) {
+    public NumberInterface subtractInternal(NumberInterface subtrahend) {
         return new PreciseNumber(value.subtract(((PreciseNumber) subtrahend).value));
     }
 
     @Override
-    public NumberInterface intPow(int exponent) {
+    public NumberInterface intPowInternal(int exponent) {
         if (exponent == 0) {
             return PreciseNumber.ONE;
         }
@@ -99,7 +116,7 @@ public class PreciseNumber implements NumberInterface {
     }
 
     @Override
-    public NumberInterface ceiling() {
+    public NumberInterface ceilingInternal() {
         String str = value.toPlainString();
         int decimalIndex = str.indexOf('.');
         if (decimalIndex != -1) {
@@ -109,23 +126,22 @@ public class PreciseNumber implements NumberInterface {
     }
 
     @Override
-    public NumberInterface floor() {
+    public NumberInterface floorInternal() {
         String str = value.toPlainString();
         int decimalIndex = str.indexOf('.');
         if (decimalIndex != -1) {
-            return new PreciseNumber(str.substring(0, decimalIndex));
+            NumberInterface floor = new PreciseNumber(str.substring(0, decimalIndex));
+            if (signum() == -1) {
+                floor = floor.subtract(ONE);
+            }
+            return floor;
         }
         return this;
     }
 
     @Override
-    public NumberInterface fractionalPart() {
-        String str = value.toPlainString();
-        int decimalIndex = str.indexOf('.');
-        if(decimalIndex != -1){
-            return new PreciseNumber(str.substring(decimalIndex + 1));
-        }
-        return ZERO;
+    public NumberInterface fractionalPartInternal() {
+        return this.subtractInternal(floorInternal());
     }
 
     @Override
@@ -134,21 +150,17 @@ public class PreciseNumber implements NumberInterface {
     }
 
     @Override
-    public NumberInterface negate() {
+    public NumberInterface negateInternal() {
         return new PreciseNumber(value.negate());
     }
 
     @Override
-    public NumberInterface promoteTo(Class<? extends NumberInterface> toClass) {
-        if (toClass == this.getClass()) {
-            return this;
-        }
-        return null;
+    public String toString() {
+        return value.round(outputContext).toString();
     }
 
     @Override
-    public String toString() {
-        BigDecimal rounded = value.setScale(getMaxPrecision() - 15, RoundingMode.HALF_UP);
-        return rounded.stripTrailingZeros().toPlainString();
+    public NumberInterface getMaxError() {
+        return new PreciseNumber(value.ulp()).multiplyInternal(TEN.intPowInternal(value.precision() - internalContext.getPrecision()));
     }
 }

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.
@@ -34,6 +35,7 @@ public class LexerTokenizer implements Tokenizer<Match<TokenType>>, PluginListen
             register(" ", TokenType.WHITESPACE);
             register(",", TokenType.COMMA);
             register("[0-9]*(\\.[0-9]+)?", TokenType.NUM);
+            register("[a-zA-Z]+", TokenType.VARIABLE);
             register("\\(", TokenType.OPEN_PARENTH);
             register("\\)", TokenType.CLOSE_PARENTH);
         }};
@@ -41,7 +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
@@ -49,9 +53,15 @@ 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()) {
+            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()) {
+            lexer.register(Pattern.sanitize(function), TokenType.TREE_VALUE_FUNCTION);
+        }
     }
 
     @Override
@@ -59,9 +69,15 @@ 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()) {
+            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()) {
+            lexer.unregister(Pattern.sanitize(function), TokenType.TREE_VALUE_FUNCTION);
+        }
     }
 
 }

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

@@ -1,13 +1,14 @@
-package org.nwapw.abacus.parsing;
+package org.nwapw.abacus.parsing.standard;
 
-import org.nwapw.abacus.Abacus;
+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.*;
 
@@ -17,10 +18,6 @@ import java.util.*;
  */
 public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListener {
 
-    /**
-     * The Abacus instance used to create number instances.
-     */
-    private Abacus abacus;
     /**
      * Map of operator precedences, loaded from the plugin operators.
      */
@@ -35,12 +32,9 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
     private Map<String, OperatorType> typeMap;
 
     /**
-     * Creates a new Shunting Yard parser with the given Abacus instance.
-     *
-     * @param abacus the abacus instance.
+     * Creates a new Shunting Yard parser.
      */
-    public ShuntingYardParser(Abacus abacus) {
-        this.abacus = abacus;
+    public ShuntingYardParser() {
         precedenceMap = new HashMap<>();
         associativityMap = new HashMap<>();
         typeMap = new HashMap<>();
@@ -61,12 +55,12 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
             Match<TokenType> match = from.remove(0);
             previousType = matchType;
             matchType = match.getType();
-            if (matchType == TokenType.NUM) {
+            if (matchType == TokenType.NUM || matchType == TokenType.VARIABLE) {
                 output.add(match);
-            } else if (matchType == TokenType.FUNCTION) {
+            } else if (matchType == TokenType.FUNCTION || matchType == TokenType.TREE_VALUE_FUNCTION) {
                 output.add(new Match<>("", TokenType.INTERNAL_FUNCTION_END));
                 tokenStack.push(match);
-            } else if (matchType == TokenType.OP) {
+            } else if (matchType == TokenType.OP || matchType == TokenType.TREE_VALUE_OP) {
                 String tokenString = match.getContent();
                 OperatorType type = typeMap.get(tokenString);
                 int precedence = precedenceMap.get(tokenString);
@@ -78,7 +72,7 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
                 }
 
                 if (tokenString.equals("-") && (previousType == null || previousType == TokenType.OP ||
-                        previousType == TokenType.OPEN_PARENTH)){
+                        previousType == TokenType.TREE_VALUE_OP || previousType == TokenType.OPEN_PARENTH)) {
                     from.add(0, new Match<>("`", TokenType.OP));
                     continue;
                 }
@@ -86,9 +80,12 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
                 while (!tokenStack.empty() && type == OperatorType.BINARY_INFIX) {
                     Match<TokenType> otherMatch = tokenStack.peek();
                     TokenType otherMatchType = otherMatch.getType();
-                    if (!(otherMatchType == TokenType.OP || otherMatchType == TokenType.FUNCTION)) break;
+                    if (!(otherMatchType == TokenType.OP ||
+                            otherMatchType == TokenType.TREE_VALUE_OP ||
+                            otherMatchType == TokenType.FUNCTION ||
+                            otherMatchType == TokenType.TREE_VALUE_FUNCTION)) break;
 
-                    if (otherMatchType == TokenType.OP) {
+                    if (otherMatchType == TokenType.OP || otherMatchType == TokenType.TREE_VALUE_OP) {
                         int otherPrecedence = precedenceMap.get(otherMatch.getContent());
                         if (otherPrecedence < precedence ||
                                 (associativity == OperatorAssociativity.RIGHT && otherPrecedence == precedence)) {
@@ -104,7 +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();
                 }
@@ -113,7 +110,10 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
         while (!tokenStack.empty()) {
             Match<TokenType> match = tokenStack.peek();
             TokenType newMatchType = match.getType();
-            if (!(newMatchType == TokenType.OP || newMatchType == TokenType.FUNCTION)) return null;
+            if (!(newMatchType == TokenType.OP ||
+                    newMatchType == TokenType.TREE_VALUE_OP ||
+                    newMatchType == TokenType.FUNCTION ||
+                    newMatchType == TokenType.TREE_VALUE_FUNCTION)) throw new ParseException("mismatched parentheses");
             output.add(tokenStack.pop());
         }
         return output;
@@ -125,45 +125,61 @@ 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) {
-        if (matches.size() == 0) return null;
+    public TreeNode constructRecursive(List<? extends Match<TokenType>> matches) {
+        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) {
+        if (matchType == TokenType.OP || matchType == TokenType.TREE_VALUE_OP) {
             String operator = match.getContent();
             OperatorType type = typeMap.get(operator);
             if (type == OperatorType.BINARY_INFIX) {
                 TreeNode right = constructRecursive(matches);
                 TreeNode left = constructRecursive(matches);
-                if (left == null || right == null) return null;
-                else return new BinaryNode(operator, left, right);
+                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;
-                else return new UnaryNode(operator, applyTo);
+                if (matchType == TokenType.OP) {
+                    return new NumberUnaryNode(operator, applyTo);
+                } else {
+                    return new TreeValueUnaryNode(operator, applyTo);
+                }
             }
         } else if (matchType == TokenType.NUM) {
-            return new NumberNode(abacus.numberFromString(match.getContent()));
-        } else if (matchType == TokenType.FUNCTION) {
+            return new NumberNode(match.getContent());
+        } else if (matchType == TokenType.VARIABLE) {
+            return new VariableNode(match.getContent());
+        } else if (matchType == TokenType.FUNCTION || matchType == TokenType.TREE_VALUE_FUNCTION) {
             String functionName = match.getContent();
-            FunctionNode node = new FunctionNode(functionName);
+            List<TreeNode> children = new ArrayList<>();
             while (!matches.isEmpty() && matches.get(0).getType() != TokenType.INTERNAL_FUNCTION_END) {
                 TreeNode argument = constructRecursive(matches);
-                if (argument == null) return null;
-                node.prependChild(argument);
+                children.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));
         Collections.reverse(tokens);
-        return constructRecursive(tokens);
+        TreeNode constructedTree = constructRecursive(tokens);
+        if(tokens.size() == 0) return constructedTree;
+        throw new ParseException("could not parse all input");
     }
 
     @Override
@@ -174,6 +190,12 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
             associativityMap.put(operator, operatorInstance.getAssociativity());
             typeMap.put(operator, operatorInstance.getType());
         }
+        for (String operator : manager.getAllTreeValueOperators()) {
+            Operator operatorInstance = manager.treeValueOperatorFor(operator);
+            precedenceMap.put(operator, operatorInstance.getPrecedence());
+            associativityMap.put(operator, operatorInstance.getAssociativity());
+            typeMap.put(operator, operatorInstance.getType());
+        }
     }
 
     @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
@@ -7,7 +7,8 @@ package org.nwapw.abacus.tree;
 public enum TokenType {
 
     INTERNAL_FUNCTION_END(-1),
-    ANY(0), WHITESPACE(1), COMMA(2), OP(3), NUM(4), FUNCTION(5), OPEN_PARENTH(6), CLOSE_PARENTH(7);
+    ANY(0), WHITESPACE(1), COMMA(2), VARIABLE(3), OP(4), TREE_VALUE_OP(4),
+    NUM(5), FUNCTION(6), TREE_VALUE_FUNCTION(6), OPEN_PARENTH(7), CLOSE_PARENTH(7);
 
     /**
      * The priority by which this token gets sorted.

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.
      */
-    protected Map<Class<? extends NumberInterface>, Function<NumberInterface, NumberInterface>> promotionPaths;
+    private Map<String, PromotionFunction> promotionPaths;
     /**
      * The implementation class for this implementation.
      */
@@ -26,8 +26,9 @@ public abstract class NumberImplementation {
 
     /**
      * Creates a new number implementation with the given data.
+     *
      * @param implementation the implementation class.
-     * @param priority the priority, higher -> more likely to be converted into.
+     * @param priority       the priority, higher means more likely to be converted into.
      */
     public NumberImplementation(Class<? extends NumberInterface> implementation, int priority) {
         this.implementation = implementation;
@@ -37,14 +38,16 @@ public abstract class NumberImplementation {
 
     /**
      * Gets the list of all promotion paths this implementation can take.
+     *
      * @return the map of documentation paths.
      */
-    public final Map<Class<? extends NumberInterface>, Function<NumberInterface, NumberInterface>> getPromotionPaths(){
+    public final Map<String, PromotionFunction> getPromotionPaths() {
         return promotionPaths;
     }
 
     /**
      * Gets the implementation class used by this implementation.
+     *
      * @return the implementation class.
      */
     public final Class<? extends NumberInterface> getImplementation() {
@@ -53,6 +56,7 @@ public abstract class NumberImplementation {
 
     /**
      * Gets the priority of this number implementation.
+     *
      * @return the priority.
      */
     public final int getPriority() {
@@ -61,6 +65,7 @@ public abstract class NumberImplementation {
 
     /**
      * Abstract function to create a new instance from a string.
+     *
      * @param string the string to create a number from.
      * @return the resulting number.
      */
@@ -68,6 +73,7 @@ public abstract class NumberImplementation {
 
     /**
      * Get the instance of pi with the given implementation.
+     *
      * @return pi
      */
     public abstract NumberInterface instanceForPi();

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

@@ -1,13 +1,13 @@
 package org.nwapw.abacus.plugin;
 
-import org.nwapw.abacus.function.Function;
-import org.nwapw.abacus.function.Operator;
+import org.nwapw.abacus.function.Documentation;
+import org.nwapw.abacus.function.DocumentationType;
+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.util.HashMap;
-import java.util.Map;
-import java.util.Set;
-
 /**
  * A plugin class that can be externally implemented and loaded via the
  * plugin manager. Plugins provide functionality to the calculator
@@ -17,18 +17,6 @@ import java.util.Set;
  */
 public abstract class Plugin {
 
-    /**
-     * A hash map of functions mapped to their string names.
-     */
-    private Map<String, Function> functions;
-    /**
-     * A hash map of operators mapped to their string names.
-     */
-    private Map<String, Operator> operators;
-    /**
-     * The map of the number implementations this plugin provides.
-     */
-    private Map<String, NumberImplementation> numberImplementations;
     /**
      * The plugin manager in which to search for functions
      * not inside this package,
@@ -49,69 +37,9 @@ public abstract class Plugin {
      */
     public Plugin(PluginManager manager) {
         this.manager = manager;
-        functions = new HashMap<>();
-        operators = new HashMap<>();
-        numberImplementations = new HashMap<>();
         enabled = false;
     }
 
-    /**
-     * Gets the list of functions provided by this plugin.
-     *
-     * @return the list of registered functions.
-     */
-    public final Set<String> providedFunctions() {
-        return functions.keySet();
-    }
-
-    /**
-     * Gets the list of functions provided by this plugin.
-     *
-     * @return the list of registered functions.
-     */
-    public final Set<String> providedOperators() {
-        return operators.keySet();
-    }
-
-    /**
-     * Gets the list of number implementations provided by this plugin.
-     *
-     * @return the list of registered number implementations.
-     */
-    public final Set<String> providedNumberImplementations(){
-        return numberImplementations.keySet();
-    }
-
-    /**
-     * Gets a function under the given function name.
-     *
-     * @param functionName the name of the function to get
-     * @return the function, or null if this plugin doesn't provide it.
-     */
-    public final Function getFunction(String functionName) {
-        return functions.get(functionName);
-    }
-
-    /**
-     * Gets an operator under the given operator name.
-     *
-     * @param operatorName the name of the operator to get.
-     * @return the operator, or null if this plugin doesn't provide it.
-     */
-    public final Operator getOperator(String operatorName) {
-        return operators.get(operatorName);
-    }
-
-    /**
-     * Gets the number implementation under the given name.
-     *
-     * @param name the name of the number implementation to look up.
-     * @return the number implementation associated with that name, or null if the plugin doesn't provide it.
-     */
-    public final NumberImplementation getNumberImplementation(String name){
-        return numberImplementations.get(name);
-    }
-
     /**
      * Enables the function, loading the necessary instances
      * of functions.
@@ -129,8 +57,6 @@ public abstract class Plugin {
     public final void disable() {
         if (!enabled) return;
         onDisable();
-        functions.clear();
-        operators.clear();
         enabled = false;
     }
 
@@ -141,8 +67,19 @@ public abstract class Plugin {
      * @param name       the name to register by.
      * @param toRegister the function implementation.
      */
-    protected final void registerFunction(String name, Function toRegister) {
-        functions.put(name, toRegister);
+    protected final void registerFunction(String name, NumberFunction toRegister) {
+        manager.registerFunction(name, toRegister);
+    }
+
+    /**
+     * To be used in load(). Registers a tree value function abstract class
+     * with the plugin internally, which makes it accessible to the plugin manager.
+     *
+     * @param name       the name to register by.
+     * @param toRegister the tree value function implementation.
+     */
+    protected final void registerTreeValueFunction(String name, TreeValueFunction toRegister) {
+        manager.registerTreeValueFunction(name, toRegister);
     }
 
     /**
@@ -153,18 +90,41 @@ public abstract class Plugin {
      * @param name     the name of the operator.
      * @param operator the operator to register.
      */
-    protected final void registerOperator(String name, Operator operator) {
-        operators.put(name, operator);
+    protected final void registerOperator(String name, NumberOperator operator) {
+        manager.registerOperator(name, operator);
+    }
+
+    /**
+     * To be used in load(). Registers an operator
+     * with the plugin internally, which makes it accessible
+     * to the plugin manager.
+     *
+     * @param name     the name of the tree value operator.
+     * @param operator the tree value operator to register.
+     */
+    protected final void registerTreeValueOperator(String name, TreeValueOperator operator) {
+        manager.registerTreeValueOperator(name, operator);
     }
 
     /**
      * To be used in load(). Registers a new number implementation with the plugin.
      * This makes it accessible to the plugin manager.
+     *
      * @param name           the name of the implementation.
      * @param implementation the actual implementation class to register.
      */
     protected final void registerNumberImplementation(String name, NumberImplementation implementation) {
-        numberImplementations.put(name, implementation);
+        manager.registerNumberImplementation(name, implementation);
+    }
+
+    /**
+     * To be used in load(). Registers a documentation instance
+     * used to explain some element of the plugin to the user.
+     *
+     * @param documentation the documentation instance.
+     */
+    protected final void registerDocumentation(Documentation documentation) {
+        manager.registerDocumentation(documentation);
     }
 
     /**
@@ -175,10 +135,22 @@ public abstract class Plugin {
      * @param name the name for which to search
      * @return the resulting function, or null if none was found for that name.
      */
-    protected final Function functionFor(String name) {
+    protected final NumberFunction functionFor(String name) {
         return manager.functionFor(name);
     }
 
+    /**
+     * Searches the PluginManager for the given function name.
+     * This can be used by the plugins internally in order to call functions
+     * they do not provide.
+     *
+     * @param name the name for which to search.
+     * @return the resulting tree value function, or null if none was found for that name.
+     */
+    protected final TreeValueFunction treeValueFunctionFor(String name) {
+        return manager.treeValueFunctionFor(name);
+    }
+
     /**
      * Searches the PluginManager for the given operator name.
      * This can be used by the plugins internally in order to call
@@ -187,10 +159,22 @@ public abstract class Plugin {
      * @param name the name for which to search
      * @return the resulting operator, or null if none was found for that name.
      */
-    protected final Operator operatorFor(String name) {
+    protected final NumberOperator operatorFor(String name) {
         return manager.operatorFor(name);
     }
 
+    /**
+     * Searches the PluginManager for the given tree value operator name.
+     * This can be used by the plugins internally in order to call
+     * operations they do not provide.
+     *
+     * @param name the name for which to search.
+     * @return the resulting tree value operator, or null if none was found for that name.
+     */
+    protected final TreeValueOperator treeValueOperatorFor(String name) {
+        return manager.treeValueOperatorFor(name);
+    }
+
     /**
      * Searches the PluginManager for the given number implementation
      * name. This can be used by the plugins internally in order to find
@@ -203,15 +187,27 @@ public abstract class Plugin {
         return manager.numberImplementationFor(name);
     }
 
+    /**
+     * Searches the PluginManager for the given documentation name and type.
+     *
+     * @param name the name for which to search.
+     * @param type the type of documentation to search for.
+     * @return the found documentation, or null if none was found.
+     */
+    protected final Documentation documentationFor(String name, DocumentationType type) {
+        return manager.documentationFor(name, type);
+    }
+
     /**
      * Searches the plugin manager for a Pi value for the given number implementation.
      * This is done so that number implementations with various degrees of precision
      * can provide their own pi values, without losing said precision by
      * promoting NaiveNumbers.
+     *
      * @param forClass the class to which to find the pi instance.
      * @return the pi value for the given class.
      */
-    protected final NumberInterface getPi(Class<? extends NumberInterface> forClass){
+    protected final NumberInterface piFor(Class<? extends NumberInterface> forClass) {
         return manager.piFor(forClass);
     }
 

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

@@ -0,0 +1,420 @@
+package org.nwapw.abacus.plugin;
+
+import org.nwapw.abacus.Abacus;
+import org.nwapw.abacus.function.Documentation;
+import org.nwapw.abacus.function.DocumentationType;
+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;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * A class that controls instances of plugins, allowing for them
+ * to interact with each other and the calculator.
+ */
+public class PluginManager {
+
+    /**
+     * List of classes loaded by this manager.
+     */
+    private Set<Class<?>> loadedPluginClasses;
+    /**
+     * A list of loaded plugins.
+     */
+    private Set<Plugin> plugins;
+    /**
+     * The map of functions registered by the plugins.
+     */
+    private Map<String, NumberFunction> registeredFunctions;
+    /**
+     * The map of tree value functions regstered by the plugins.
+     */
+    private Map<String, TreeValueFunction> registeredTreeValueFunctions;
+    /**
+     * The map of operators registered by the plugins
+     */
+    private Map<String, NumberOperator> registeredOperators;
+    /**
+     * The map of tree value operators registered by the plugins.
+     */
+    private Map<String, TreeValueOperator> registeredTreeValueOperators;
+    /**
+     * The map of number implementations registered by the plugins.
+     */
+    private Map<String, NumberImplementation> registeredNumberImplementations;
+    /**
+     * The map of documentation for functions registered by the plugins.
+     */
+    private Set<Documentation> registeredDocumentation;
+    /**
+     * The list of number implementation names.
+     */
+    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.
+     */
+    private Map<Class<? extends NumberInterface>, NumberInterface> cachedPi;
+    /**
+     * The list of plugin listeners attached to this instance.
+     */
+    private Set<PluginListener> listeners;
+    /**
+     * The abacus instance used to access other
+     * components of the application.
+     */
+    private Abacus abacus;
+
+    /**
+     * Creates a new plugin manager.
+     *
+     * @param abacus the abacus instance.
+     */
+    public PluginManager(Abacus abacus) {
+        this.abacus = abacus;
+        loadedPluginClasses = new HashSet<>();
+        plugins = new HashSet<>();
+        registeredFunctions = new HashMap<>();
+        registeredTreeValueFunctions = new HashMap<>();
+        registeredOperators = new HashMap<>();
+        registeredTreeValueOperators = new HashMap<>();
+        registeredNumberImplementations = new HashMap<>();
+        registeredDocumentation = new HashSet<>();
+        interfaceImplementations = new HashMap<>();
+        interfaceImplementationNames = new HashMap<>();
+        cachedPi = new HashMap<>();
+        listeners = new HashSet<>();
+    }
+
+    /**
+     * Registers a function under the given name.
+     *
+     * @param name     the name of the function.
+     * @param function the function to register.
+     */
+    public void registerFunction(String name, NumberFunction function) {
+        registeredFunctions.put(name, function);
+    }
+
+    /**
+     * Registers a tree value function under the given name.
+     *
+     * @param name     the name of the function.
+     * @param function the function to register.
+     */
+    public void registerTreeValueFunction(String name, TreeValueFunction function) {
+        registeredTreeValueFunctions.put(name, function);
+    }
+
+    /**
+     * Registers an operator under the given name.
+     *
+     * @param name     the name of the operator.
+     * @param operator the operator to register.
+     */
+    public void registerOperator(String name, NumberOperator operator) {
+        registeredOperators.put(name, operator);
+    }
+
+    /**
+     * Registers a tree value operator under the given name.
+     *
+     * @param name     the name of the tree value operator.
+     * @param operator the tree value operator to register.
+     */
+    public void registerTreeValueOperator(String name, TreeValueOperator operator) {
+        registeredTreeValueOperators.put(name, operator);
+    }
+
+    /**
+     * Registers a number implementation under the given name.
+     *
+     * @param name           the name of the number implementation.
+     * @param implementation the number implementation to register.
+     */
+    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());
+    }
+
+    /**
+     * Registers the given documentation with the plugin manager,
+     * making it accessible to the plugin manager etc.
+     *
+     * @param documentation the documentation to register.
+     */
+    public void registerDocumentation(Documentation documentation) {
+        registeredDocumentation.add(documentation);
+    }
+
+    /**
+     * Gets the function registered under the given name.
+     *
+     * @param name the name of the function.
+     * @return the function, or null if it was not found.
+     */
+    public NumberFunction functionFor(String name) {
+        return registeredFunctions.get(name);
+    }
+
+    /**
+     * Gets the tree value function registered under the given name.
+     *
+     * @param name the name of the function.
+     * @return the function, or null if it was not found.
+     */
+    public TreeValueFunction treeValueFunctionFor(String name) {
+        return registeredTreeValueFunctions.get(name);
+    }
+
+    /**
+     * Gets the operator registered under the given name.
+     *
+     * @param name the name of the operator.
+     * @return the operator, or null if it was not found.
+     */
+    public NumberOperator operatorFor(String name) {
+        return registeredOperators.get(name);
+    }
+
+    /**
+     * Gets the tree value operator registered under the given name.
+     *
+     * @param name the name of the tree value operator.
+     * @return the operator, or null if it was not found.
+     */
+    public TreeValueOperator treeValueOperatorFor(String name) {
+        return registeredTreeValueOperators.get(name);
+    }
+
+    /**
+     * Gets the number implementation registered under the given name.
+     *
+     * @param name the name of the number implementation.
+     * @return the number implementation, or null if it was not found.
+     */
+    public NumberImplementation numberImplementationFor(String name) {
+        return registeredNumberImplementations.get(name);
+    }
+
+    /**
+     * Gets the documentation for the given entity of the given type.
+     *
+     * @param name the name of the entity to search for.
+     * @param type the type that this entity is, to filter out similarly named documentation.
+     * @return the documentation object.
+     */
+    public Documentation documentationFor(String name, DocumentationType type) {
+        Documentation toReturn = null;
+        for (Documentation entry : registeredDocumentation) {
+            if (entry.getCodeName().equals(name) && entry.getType() == type) {
+                toReturn = entry;
+                break;
+            }
+        }
+        return toReturn;
+    }
+
+    /**
+     * Gets the number implementation for the given implementation class.
+     *
+     * @param name the class for which to find the implementation.
+     * @return the implementation.
+     */
+    public NumberImplementation interfaceImplementationFor(Class<? extends NumberInterface> name) {
+        return interfaceImplementations.get(name);
+    }
+
+    /**
+     * Gets the number implementation name for the given implementation class.
+     *
+     * @param name the class for which to find the implementation name.
+     * @return the implementation name.
+     */
+    public String interfaceImplementationNameFor(Class<? extends NumberInterface> name) {
+        return interfaceImplementationNames.get(name);
+    }
+
+    /**
+     * Gets the mathematical constant pi for the given implementation class.
+     *
+     * @param forClass the class for which to find pi.
+     * @return pi
+     */
+    public NumberInterface piFor(Class<? extends NumberInterface> forClass) {
+        return cachedPi.get(forClass);
+    }
+
+    /**
+     * Adds an instance of Plugin that already has been instantiated.
+     *
+     * @param plugin the plugin to add.
+     */
+    public void addInstantiated(Plugin plugin) {
+        if (loadedPluginClasses.contains(plugin.getClass())) return;
+        plugins.add(plugin);
+        loadedPluginClasses.add(plugin.getClass());
+    }
+
+    /**
+     * Instantiates a class of plugin, and adds it to this
+     * plugin manager.
+     *
+     * @param newClass the new class to instantiate.
+     */
+    public void addClass(Class<?> newClass) {
+        if (!Plugin.class.isAssignableFrom(newClass) || newClass == Plugin.class) return;
+        try {
+            addInstantiated((Plugin) newClass.getConstructor(PluginManager.class).newInstance(this));
+        } catch (InstantiationException | IllegalAccessException | NoSuchMethodException | InvocationTargetException e) {
+            e.printStackTrace();
+        }
+    }
+
+    /**
+     * Removes the plugin with the given class from the manager.
+     *
+     * @param toRemove the plugin to remove.
+     */
+    public void removeClass(Class<? extends Plugin> toRemove) {
+        if (!loadedPluginClasses.contains(toRemove)) return;
+        plugins.removeIf(plugin -> plugin.getClass() == toRemove);
+        loadedPluginClasses.remove(toRemove);
+    }
+
+    /**
+     * Removes all plugins from this plugin manager.
+     */
+    public void removeAll() {
+        loadedPluginClasses.clear();
+        plugins.clear();
+    }
+
+    /**
+     * Loads all the plugins in the PluginManager.
+     */
+    public void load() {
+        Set<String> disabledPlugins = abacus.getConfiguration().getDisabledPlugins();
+        for (Plugin plugin : plugins) {
+            if (disabledPlugins.contains(plugin.getClass().getName())) continue;
+            plugin.enable();
+        }
+        listeners.forEach(e -> e.onLoad(this));
+    }
+
+    /**
+     * Unloads all the plugins in the PluginManager.
+     */
+    public void unload() {
+        listeners.forEach(e -> e.onUnload(this));
+        Set<String> disabledPlugins = abacus.getConfiguration().getDisabledPlugins();
+        for (Plugin plugin : plugins) {
+            if (disabledPlugins.contains(plugin.getClass().getName())) continue;
+            plugin.disable();
+        }
+        registeredFunctions.clear();
+        registeredTreeValueFunctions.clear();
+        registeredOperators.clear();
+        registeredTreeValueOperators.clear();
+        registeredNumberImplementations.clear();
+        registeredDocumentation.clear();
+        interfaceImplementationNames.clear();
+        interfaceImplementations.clear();
+        cachedPi.clear();
+        listeners.forEach(e -> e.onUnload(this));
+    }
+
+    /**
+     * Reloads all the plugins in the PluginManager.
+     */
+    public void reload() {
+        unload();
+        load();
+    }
+
+    /**
+     * Gets all the functions loaded by the Plugin Manager.
+     *
+     * @return the set of all functions that were loaded.
+     */
+    public Set<String> getAllFunctions() {
+        return registeredFunctions.keySet();
+    }
+
+    /**
+     * Gets all the tree vlaue functions loaded by the PluginManager.
+     *
+     * @return the set of all the tree value functions that were loaded.
+     */
+    public Set<String> getAllTreeValueFunctions() {
+        return registeredTreeValueFunctions.keySet();
+    }
+
+    /**
+     * Gets all the operators loaded by the Plugin Manager.
+     *
+     * @return the set of all operators that were loaded.
+     */
+    public Set<String> getAllOperators() {
+        return registeredOperators.keySet();
+    }
+
+    /**
+     * Gets all the tree value operators loaded by the PluginManager.
+     *
+     * @return the set of all tree value operators that were loaded.
+     */
+    public Set<String> getAllTreeValueOperators() {
+        return registeredTreeValueOperators.keySet();
+    }
+
+    /**
+     * Gets all the number implementations loaded by the Plugin Manager.
+     *
+     * @return the set of all implementations that were loaded.
+     */
+    public Set<String> getAllNumberImplementations() {
+        return registeredNumberImplementations.keySet();
+    }
+
+    /**
+     * Adds a plugin change listener to this plugin manager.
+     *
+     * @param listener the listener to add.
+     */
+    public void addListener(PluginListener listener) {
+        listeners.add(listener);
+    }
+
+    /**
+     * Remove the plugin change listener from this plugin manager.
+     *
+     * @param listener the listener to remove.
+     */
+    public void removeListener(PluginListener listener) {
+        listeners.remove(listener);
+    }
+
+    /**
+     * Gets a list of all the plugin class files that have been
+     * added to the plugin manager.
+     *
+     * @return the list of all the added plugin classes.
+     */
+    public Set<Class<?>> getLoadedPluginClasses() {
+        return loadedPluginClasses;
+    }
+    
+}

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

@@ -0,0 +1,679 @@
+package org.nwapw.abacus.plugin.standard;
+
+import org.jetbrains.annotations.NotNull;
+import org.nwapw.abacus.context.MutableEvaluationContext;
+import org.nwapw.abacus.context.PluginEvaluationContext;
+import org.nwapw.abacus.function.Documentation;
+import org.nwapw.abacus.function.DocumentationType;
+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.NumberInterface;
+import org.nwapw.abacus.number.standard.NaiveNumber;
+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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1 && params[0].compareTo(context.getInheritedNumberImplementation().instanceForString("0")) > 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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 context
+         * @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(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1
+                    && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) <= 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) <= 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) >= 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) >= 0;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext context, NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        public NumberInterface applyInternal(PluginEvaluationContext 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(PluginEvaluationContext 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(PluginEvaluationContext 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/kotlin/org/nwapw/abacus/Abacus.kt

@@ -0,0 +1,112 @@
+package org.nwapw.abacus
+
+import org.nwapw.abacus.config.Configuration
+import org.nwapw.abacus.context.EvaluationContext
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.number.promotion.PromotionManager
+import org.nwapw.abacus.parsing.TreeBuilder
+import org.nwapw.abacus.parsing.standard.LexerTokenizer
+import org.nwapw.abacus.parsing.standard.ShuntingYardParser
+import org.nwapw.abacus.plugin.PluginManager
+import org.nwapw.abacus.plugin.standard.StandardPlugin
+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, abacus = this)
+    /**
+     * 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(){
+        with(mutableContext){
+            clearVariables()
+            clearDefinitions()
+        }
+        pluginManager.reload()
+        mutableContext.numberImplementation = pluginManager.numberImplementationFor(configuration.numberImplementation)
+                ?: StandardPlugin.IMPLEMENTATION_NAIVE
+    }
+    /**
+     * 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 evaluationValue = tree.reduce(context)
+        return EvaluationResult(evaluationValue, 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 +1,85 @@
+package org.nwapw.abacus.context
+
+import org.nwapw.abacus.Abacus
+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 abacus the abacus instance used by this reducer.
+ */
+abstract class EvaluationContext(val parent: EvaluationContext? = null,
+                                 open val numberImplementation: NumberImplementation? = null,
+                                 open val abacus: Abacus? = null): Reducer<NumberInterface> {
+
+    /**
+     * 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 Abacus instance inherited from this context's parent.
+     */
+    val inheritedAbacus: Abacus
+            by ChainSearchDelegate { abacus }
+
+    /**
+     * 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 +1,91 @@
+package org.nwapw.abacus.context
+
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.exception.NumberReducerException
+import org.nwapw.abacus.exception.ReductionException
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.NumberImplementation
+import org.nwapw.abacus.tree.nodes.*
+
+/**
+ * A reduction context that is mutable.
+ *
+ * @param parent the parent of this context.
+ * @param numberImplementation the number implementation used in this context.
+ * @param abacus the abacus instance used.
+ */
+class MutableEvaluationContext(parent: EvaluationContext? = null,
+                               numberImplementation: NumberImplementation? = null,
+                               abacus: Abacus? = null) :
+        PluginEvaluationContext(parent, numberImplementation, abacus) {
+
+    override var numberImplementation: NumberImplementation? = super.numberImplementation
+    override var abacus: Abacus? = super.abacus
+
+    /**
+     * 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
+        for(name in other.variables) {
+            setVariable(name, other.getVariable(name) ?: continue)
+        }
+        for(name in other.definitions) {
+            setDefinition(name, other.getDefinition(name) ?: continue)
+        }
+    }
+
+    override fun reduceNode(treeNode: TreeNode, vararg children: Any): NumberInterface {
+        val oldNumberImplementation = numberImplementation
+        val abacus = inheritedAbacus
+        val promotionManager = abacus.promotionManager
+        val toReturn = when(treeNode){
+            is NumberNode -> {
+                inheritedNumberImplementation.instanceForString(treeNode.number)
+            }
+            is VariableNode -> {
+                val variable = getVariable(treeNode.variable)
+                if(variable != null) return variable
+                val definition = getDefinition(treeNode.variable)
+                if(definition != null) return definition.reduce(this)
+                throw NumberReducerException("variable is not defined.")
+            }
+            is NumberUnaryNode -> {
+                val child = children[0] as NumberInterface
+                numberImplementation = abacus.pluginManager.interfaceImplementationFor(child.javaClass)
+                abacus.pluginManager.operatorFor(treeNode.operation)
+                        .apply(this, child)
+            }
+            is NumberBinaryNode -> {
+                val left = children[0] as NumberInterface
+                val right = children[1] as NumberInterface
+                val promotionResult = promotionManager.promote(left, right)
+                numberImplementation = promotionResult.promotedTo
+                abacus.pluginManager.operatorFor(treeNode.operation).apply(this, *promotionResult.items)
+            }
+            is NumberFunctionNode -> {
+                val promotionResult = promotionManager
+                        .promote(*children.map { it as NumberInterface }.toTypedArray())
+                numberImplementation = promotionResult.promotedTo
+                abacus.pluginManager.functionFor(treeNode.callTo).apply(this, *promotionResult.items)
+            }
+            is TreeValueUnaryNode -> {
+                abacus.pluginManager.treeValueOperatorFor(treeNode.operation)
+                        .apply(this, treeNode.applyTo)
+            }
+            is TreeValueBinaryNode -> {
+                abacus.pluginManager.treeValueOperatorFor(treeNode.operation)
+                        .apply(this, treeNode.left, treeNode.right)
+            }
+            is TreeValueFunctionNode -> {
+                abacus.pluginManager.treeValueFunctionFor(treeNode.callTo)
+                        .apply(this, *treeNode.children.toTypedArray())
+            }
+            else -> throw ReductionException("unrecognized tree node.")
+        }
+        numberImplementation = oldNumberImplementation
+        return toReturn
+    }
+
+}

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

@@ -0,0 +1,58 @@
+package org.nwapw.abacus.context
+
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.NumberImplementation
+import org.nwapw.abacus.tree.nodes.TreeNode
+
+/**
+ * An evaluation context with limited mutability.
+ *
+ * An evaluation context that is mutable but in a limited way, that is, not allowing the modifications
+ * of variables whose changes might cause issues outside of the function. An example of this would be
+ * the modification of the [numberImplementation], which would cause code paths such as the parsing
+ * of NumberNodes to produce a different type of number than if the function did not run, whcih is unacceptable.
+ *
+ * @param parent the parent of this context.
+ * @param numberImplementation the number implementation used in this context.
+ * @param abacus the abacus instance used.
+ */
+abstract class PluginEvaluationContext(parent: EvaluationContext? = null,
+                                       numberImplementation: NumberImplementation? = null,
+                                       abacus: Abacus? = null) :
+        EvaluationContext(parent, numberImplementation, abacus) {
+
+    /**
+     * 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

@@ -0,0 +1,45 @@
+package org.nwapw.abacus.function
+
+import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.context.PluginEvaluationContext
+import org.nwapw.abacus.exception.DomainException
+
+/**
+ * A class that can be applied to arguments.
+ *
+ * Applicable is a class that represents something that can be applied to one or more
+ * arguments of the same type, and returns a single value from that application.
+ * @param <T> the type of the parameters passed to this applicable.
+ * @param <O> the return type of the applicable.
+ */
+interface Applicable<in T : Any, out O : Any> {
+
+    /**
+     * Checks if the given applicable can be used with the given parameters.
+     * @param params the parameter array to verify for compatibility.
+     * @return whether the array can be used with applyInternal.
+     */
+    fun matchesParams(context: PluginEvaluationContext, params: Array<out T>): Boolean
+
+    /**
+     * Applies the applicable object to the given parameters,
+     * without checking for compatibility.
+     * @param params the parameters to apply to.
+     * @return the result of the application.
+     */
+    fun applyInternal(context: PluginEvaluationContext, params: Array<out T>): O
+
+    /**
+     * If the parameters can be used with this applicable, returns
+     * the result of the application of the applicable to the parameters.
+     * Otherwise, returns null.
+     * @param params the parameters to apply to.
+     * @return the result of the operation, or null if parameters do not match.
+     */
+    fun apply(context: PluginEvaluationContext, vararg params: T): O {
+        if (!matchesParams(context, params))
+            throw DomainException("parameters do not match function requirements.")
+        return applyInternal(context, params)
+    }
+
+}

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

@@ -0,0 +1,26 @@
+package org.nwapw.abacus.function
+
+/**
+ * A data class used for storing information about a function.
+ *
+ * The Documentation class holds the information necessary to display the information
+ * about a function to the user.
+ *
+ * @param codeName the name of the function as it occurs in code.
+ * @param name the name of the function in English.
+ * @param description the short description of this function.
+ * @param longDescription the full description of this function.
+ * @param type the things this documentation maps to.
+ */
+data class Documentation(val codeName: String, val name: String,
+                         val description: String, val longDescription: String,
+                         val type: DocumentationType) {
+
+    fun matches(other: String): Boolean {
+        return codeName.toLowerCase().contains(other.toLowerCase()) ||
+                name.toLowerCase().contains(other.toLowerCase()) ||
+                description.toLowerCase().contains(other.toLowerCase()) ||
+                longDescription.toLowerCase().contains(other.toLowerCase())
+    }
+
+}

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

@@ -0,0 +1,13 @@
+package org.nwapw.abacus.function
+
+/**
+ * A single operator that can be used by Abacus.
+ *
+ * This is a class that holds the information about a single operator, such as a plus or minus.
+ *
+ * @param associativity the associativity of this operator, used for order of operations;.
+ * @param type the type of this operator, used for parsing (infix / prefix / postfix and binary / unary)
+ * @param precedence the precedence of this operator, used for order of operations.
+ */
+open class Operator(val associativity: OperatorAssociativity, val type: OperatorType,
+                    val precedence: Int)

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

@@ -0,0 +1,12 @@
+package org.nwapw.abacus.function.interfaces
+
+import org.nwapw.abacus.function.Applicable
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * A function that operates on numbers.
+ *
+ * This function takes some number of input NumberInterfaces and returns
+ * another NumberInterface as a result.
+ */
+abstract class NumberFunction : Applicable<NumberInterface, NumberInterface>

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

@@ -0,0 +1,20 @@
+package org.nwapw.abacus.function.interfaces
+
+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
+
+/**
+ * An operator that operates on NumberImplementations.
+ *
+ * This is simply an alias for Operator<NumberInterface, NumberInterface>.
+ * @param associativity the associativity of the operator.
+ * @param type the type of the operator (binary, unary, etc)
+ * @param precedence the precedence of the operator.
+ */
+abstract class NumberOperator(associativity: OperatorAssociativity, type: OperatorType,
+                              precedence: Int) :
+        Operator(associativity, type, precedence),
+        Applicable<NumberInterface, NumberInterface>

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

@@ -0,0 +1,13 @@
+package org.nwapw.abacus.function.interfaces
+
+import org.nwapw.abacus.function.Applicable
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.tree.nodes.TreeNode
+
+/**
+ * A function that operates on trees.
+ *
+ * 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 : Applicable<TreeNode, NumberInterface>

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

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.function.interfaces
+
+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.nodes.TreeNode
+
+/**
+ * An operator that operates on trees.
+ *
+ * This operator operates on parse trees, returning, however a number.
+ * @param associativity the associativity of the operator.
+ * @param type the type of the operator (infix, postfix, etc)
+ * @param precedence the precedence of the operator.
+ */
+abstract class TreeValueOperator(associativity: OperatorAssociativity, type: OperatorType,
+                                 precedence: Int) :
+        Operator(associativity, type, precedence),
+        Applicable<TreeNode, NumberInterface>

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

@@ -0,0 +1,276 @@
+package org.nwapw.abacus.number
+
+import org.nwapw.abacus.exception.ComputationInterruptedException
+import org.nwapw.abacus.number.range.NumberRangeBuilder
+
+abstract class NumberInterface: Comparable<NumberInterface> {
+
+    /**
+     * Check if the thread was interrupted and
+     * throw an exception to end the computation.
+     */
+    private fun checkInterrupted(){
+        if(Thread.currentThread().isInterrupted)
+            throw ComputationInterruptedException()
+    }
+
+    /**
+     * Returns the integer representation of this number, discarding any fractional part,
+     * if int can hold the value.
+     *
+     * @return the integer value of this number.
+     */
+    abstract fun intValue(): Int
+    /**
+     * Same as Math.signum().
+     *
+     * @return 1 if this number is positive, -1 if this number is negative, 0 if this number is 0.
+     */
+    abstract fun signum(): Int
+
+    /**
+     * The maximum precision to which this number operates.
+     */
+    abstract val maxPrecision: Int
+    /**
+     * Returns the smallest error this instance can tolerate depending
+     * on its precision and value.
+     */
+    abstract val maxError: NumberInterface
+
+    /**
+     * Adds this number to another, returning
+     * a new number instance.
+     *
+     * @param summand the summand
+     * @return the result of the summation.
+     */
+    abstract fun addInternal(summand: NumberInterface): NumberInterface
+    /**
+     * Subtracts another number from this number,
+     * a new number instance.
+     *
+     * @param subtrahend the subtrahend.
+     * @return the result of the subtraction.
+     */
+    abstract fun subtractInternal(subtrahend: NumberInterface): NumberInterface
+    /**
+     * Multiplies this number by another, returning
+     * a new number instance.
+     *
+     * @param multiplier the multiplier
+     * @return the result of the multiplication.
+     */
+    abstract fun multiplyInternal(multiplier: NumberInterface): NumberInterface
+    /**
+     * Divides this number by another, returning
+     * a new number instance.
+     *
+     * @param divisor the divisor
+     * @return the result of the division.
+     */
+    abstract fun divideInternal(divisor: NumberInterface): NumberInterface
+    /**
+     * Returns a new instance of this number with
+     * the sign flipped.
+     *
+     * @return the new instance.
+     */
+    abstract fun negateInternal(): NumberInterface
+    /**
+     * Raises this number to an integer power.
+     *
+     * @param exponent the exponent to which to take the number.
+     * @return the resulting value.
+     */
+    abstract fun intPowInternal(pow: Int): NumberInterface
+    /**
+     * Returns the least integer greater than or equal to the number.
+     *
+     * @return the least integer greater or equal to the number, if int can hold the value.
+     */
+    abstract fun ceilingInternal(): NumberInterface
+    /**
+     * Return the greatest integer less than or equal to the number.
+     *
+     * @return the greatest integer smaller or equal the number.
+     */
+    abstract fun floorInternal(): NumberInterface
+    /**
+     * Returns the fractional part of the number.
+     *
+     * @return the fractional part of the number.
+     */
+    abstract fun fractionalPartInternal(): NumberInterface
+
+    /**
+     * Adds this number to another, returning
+     * a new number instance. Also, checks if the
+     * thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @param summand the summand
+     * @return the result of the summation.
+     */
+    fun add(summand: NumberInterface): NumberInterface {
+        checkInterrupted()
+        return addInternal(summand)
+    }
+
+    /**
+     * Subtracts another number from this number,
+     * a new number instance. Also, checks if the
+     * thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @param subtrahend the subtrahend.
+     * @return the result of the subtraction.
+     */
+    fun subtract(subtrahend: NumberInterface): NumberInterface {
+        checkInterrupted()
+        return subtractInternal(subtrahend)
+    }
+
+    /**
+     * Multiplies this number by another, returning
+     * a new number instance. Also, checks if the
+     * thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @param multiplier the multiplier
+     * @return the result of the multiplication.
+     */
+    fun multiply(multiplier: NumberInterface): NumberInterface {
+        checkInterrupted()
+        return multiplyInternal(multiplier)
+    }
+
+    /**
+     * Divides this number by another, returning
+     * a new number instance. Also, checks if the
+     * thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @param divisor the divisor
+     * @return the result of the division.
+     */
+    fun divide(divisor: NumberInterface): NumberInterface {
+        checkInterrupted()
+        return divideInternal(divisor)
+    }
+
+    /**
+     * Returns a new instance of this number with
+     * the sign flipped. Also, checks if the
+     * thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @return the new instance.
+     */
+    fun negate(): NumberInterface {
+        checkInterrupted()
+        return negateInternal()
+    }
+
+    /**
+     * Raises this number to an integer power. Also, checks if the
+     * thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @param exponent the exponent to which to take the number.
+     * @return the resulting value.
+     */
+    fun intPow(exponent: Int): NumberInterface {
+        checkInterrupted()
+        return intPowInternal(exponent)
+    }
+
+    /**
+     * Returns the least integer greater than or equal to the number.
+     * Also, checks if the thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @return the least integer bigger or equal to the number.
+     */
+    fun ceiling(): NumberInterface {
+        checkInterrupted()
+        return ceilingInternal()
+    }
+
+    /**
+     * Return the greatest integer less than or equal to the number.
+     * Also, checks if the thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @return the greatest int smaller than or equal to the number.
+     */
+    fun floor(): NumberInterface {
+        checkInterrupted()
+        return floorInternal()
+    }
+
+    /**
+     * Returns the fractional part of the number, specifically x - floor(x).
+     * Also, checks if the thread has been interrupted,
+     * and if so, throws an exception.
+     *
+     * @return the fractional part of the number.
+     */
+    fun fractionalPart(): NumberInterface {
+        checkInterrupted()
+        return fractionalPartInternal()
+    }
+
+    /**
+     * Checks whether the given number is an integer or not.
+     *
+     * @return whether the number is an integer or not.
+     */
+    fun isInteger() = fractionalPart().signum() == 0
+
+    /**
+     * Returns a NumberRangeBuilder object, which is used to create a range.
+     * The reason that this returns a builder and not an actual range is that
+     * the NumberRange needs to promote values passed to it, which
+     * requires an abacus instance.
+     * @param other the value at the bottom of the range.
+     * @return the resulting range builder.
+     */
+    operator fun rangeTo(other: NumberInterface) = NumberRangeBuilder(this, other)
+
+    /**
+     * Plus operator overloaded to allow "nice" looking math.
+     * @param other the value to add to this number.
+     * @return the result of the addition.
+     */
+    operator fun plus(other: NumberInterface) = add(other)
+    /**
+     * Minus operator overloaded to allow "nice" looking math.
+     * @param other the value to subtract to this number.
+     * @return the result of the subtraction.
+     */
+    operator fun minus(other: NumberInterface) = subtract(other)
+    /**
+     * Times operator overloaded to allow "nice" looking math.
+     * @param other the value to multiply this number by.
+     * @return the result of the multiplication.
+     */
+    operator fun times(other: NumberInterface) = multiply(other)
+    /**
+     * Divide operator overloaded to allow "nice" looking math.
+     * @param other the value to divide this number by.
+     * @return the result of the division.
+     */
+    operator fun div(other: NumberInterface) = divide(other)
+    /**
+     * The plus operator.
+     * @return this number.
+     */
+    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 java.util.List;
+import org.nwapw.abacus.tree.nodes.TreeNode
 
 /**
- * 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.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+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, 1) {
+
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+    override fun applyInternal(context: PluginEvaluationContext, 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.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+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, 3) {
+
+    override fun matchesParams(context: PluginEvaluationContext, 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: PluginEvaluationContext, 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.PluginEvaluationContext
+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: PluginEvaluationContext, params: Array<out TreeNode>) =
+            params.size == 2 && params[0] is VariableNode
+
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out TreeNode>): NumberInterface {
+        val assignTo = (params[0] as VariableNode).variable
+        context.setDefinition(assignTo, params[1])
+        return params[1].reduce(context)
+    }
+
+}

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.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+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, 2) {
+
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+    override fun applyInternal(context: PluginEvaluationContext, 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.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+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: PluginEvaluationContext, params: Array<out NumberInterface>) =
+        params.size == 1
+                && params[0].isInteger()
+                && params[0].signum() >= 0
+
+    override fun applyInternal(context: PluginEvaluationContext, 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.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+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, 2) {
+
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params[0] * params[1]
+
+}

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

@@ -0,0 +1,26 @@
+package org.nwapw.abacus.plugin.standard.operator
+
+import org.nwapw.abacus.context.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.standard.StandardPlugin.OP_FACTORIAL
+import org.nwapw.abacus.plugin.standard.StandardPlugin.OP_NPR
+
+/**
+ * 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, 1) {
+
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2 && params[0].isInteger()
+                    && params[1].isInteger()
+
+    override fun applyInternal(context: PluginEvaluationContext, 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.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+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, 1) {
+
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 1
+
+    override fun applyInternal(context: PluginEvaluationContext, 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.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+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, 1) {
+
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2 && params[0].isInteger()
+                    && params[1].isInteger()
+
+    override fun applyInternal(context: PluginEvaluationContext, 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.PluginEvaluationContext
+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: PluginEvaluationContext, params: Array<out TreeNode>) =
+            params.size == 2 && params[0] is VariableNode
+
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out TreeNode>): NumberInterface {
+        val assignTo = (params[0] as VariableNode).variable
+        val value = params[1].reduce(context)
+        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.PluginEvaluationContext
+import org.nwapw.abacus.function.OperatorAssociativity
+import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
+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, 1) {
+
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params[0] - params[1]
+
+}

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

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.tree
+
+import org.nwapw.abacus.tree.nodes.TreeNode
+
+/**
+ * Reducer interface that takes a tree and returns a single value.
+ *
+ * The reducer walks the tree, visiting the children first, converting them into
+ * a value, and then attempts to reduce the parent. Eventually, the single final value is returned.
+ */
+interface Reducer<out T> {
+
+    /**
+     * Reduces the given tree node, given its already reduced children.
+     *
+     * @param treeNode the tree node to reduce.
+     * @param children the list of children, of type T.
+     */
+    fun reduceNode(treeNode: TreeNode, vararg children: Any): T
+
+}

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

@@ -0,0 +1,20 @@
+package org.nwapw.abacus.tree.nodes
+
+/**
+ * A tree node that holds a binary operation.
+ *
+ * This node represents any binary operation, such as binary infix or binary postfix. The only
+ * currently implemented into Abacus is binary infix, but that has more to do with the parser than
+ * this class, which doesn't care about the order that its operation and nodes were found in text.
+ *
+ * @param operation the operation this node performs on its children.
+ * @param left the left node.
+ * @param right the right node.
+ */
+abstract class BinaryNode(val operation: String, val left: TreeNode, val right: TreeNode) : TreeNode() {
+
+    override fun toString(): String {
+        return "(" + left.toString() + operation + right.toString() + ")"
+    }
+
+}

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

@@ -0,0 +1,25 @@
+package org.nwapw.abacus.tree.nodes
+
+/**
+ * Represents a more generic function call.
+ *
+ * This class does not specify how it should be reduced, allowing other classes
+ * 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, val children: List<TreeNode>) : TreeNode() {
+
+    override fun toString(): String {
+        val buffer = StringBuffer()
+        buffer.append(callTo)
+        buffer.append("(")
+        for (i in 0 until children.size) {
+            buffer.append(children[i].toString())
+            buffer.append(if (i != children.size - 1) ", " else ")")
+        }
+        return buffer.toString()
+    }
+
+}

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

@@ -0,0 +1,24 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A binary operator node that reduces its children.
+ *
+ * NumberBinaryNode operates by simply reducing its children and
+ * then using the result of that reduction to reduce itself.
+ *
+ * @param operation the operation this node performs.
+ * @param left the left child of this node.
+ * @param right the right child of this node.
+ */
+class NumberBinaryNode(operation: String, left: TreeNode, right: TreeNode)
+    : BinaryNode(operation, left, right) {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
+        val left = left.reduce(reducer)
+        val right = right.reduce(reducer)
+        return reducer.reduceNode(this, left, right)
+    }
+
+}

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

@@ -0,0 +1,20 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A tree node that holds a function call.
+ *
+ * The function call node can hold any number of children, and passes the to the appropriate reducer,
+ * but that is its sole purpose.
+ *
+ * @param function the function string.
+ */
+class NumberFunctionNode(function: String, children: List<TreeNode>) : CallNode(function, children) {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
+        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

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A tree node that holds a single number value.
+ *
+ * This is a tree node that holds a single NumberInterface, which represents any number,
+ * and is not defined during compile time.
+ *
+ * @number the number value of this node.
+ */
+class NumberNode(val number: String) : TreeNode() {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
+        return reducer.reduceNode(this)
+    }
+
+    override fun toString(): String {
+        return number
+    }
+
+}

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

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A unary operator node that reduces its children.
+ *
+ * NumberUnaryNode operates by simply reducing its child,
+ * and using the result of that reduction to reduce itself.
+ * @param operation the operation this node performs.
+ * @param child the child this node should be applied to.
+ */
+class NumberUnaryNode(operation: String, child: TreeNode)
+    : UnaryNode(operation, child) {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
+        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

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A tree node that represents a binary tree value operator.
+ *
+ *
+ * The tree value operators operate on trees, and so this
+ * node does not reduce its children. It is up to the implementation to handle
+ * reduction.
+ * @param operation the operation this node performs.
+ * @param left the left child of this node.
+ * @param right the right child of this node.
+ */
+class TreeValueBinaryNode(operation: String, left: TreeNode, right: TreeNode)
+    : BinaryNode(operation, left, right) {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
+        return reducer.reduceNode(this)
+    }
+
+}

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

@@ -0,0 +1,18 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A tree node that represents a tree value function call.
+ *
+ * This is in many ways similar to a simple FunctionNode, and the distinction
+ * is mostly to help the reducer. Besides that, this class also does not
+ * even attempt to reduce its children.
+ */
+class TreeValueFunctionNode(name: String, children: List<TreeNode>) : CallNode(name, children) {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
+        return reducer.reduceNode(this)
+    }
+
+}

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

@@ -0,0 +1,21 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A tree node that represents a unary tree value operator.
+ *
+ * The tree value operators operate on trees, and so this
+ * node does not reduce its children. It is up to the implementation to handle
+ * reduction.
+ * @param operation the operation this node performs.
+ * @param child the node the operation should be applied to.
+ */
+class TreeValueUnaryNode(operation: String, child: TreeNode)
+    : UnaryNode(operation, child) {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
+        return reducer.reduceNode(this)
+    }
+
+}

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

@@ -0,0 +1,18 @@
+package org.nwapw.abacus.tree.nodes
+
+/**
+ * A tree node that holds a unary operation.
+ *
+ * This node holds a single operator applied to a single parameter, and does not care
+ * whether the operation was found before or after the parameter in the text.
+ *
+ * @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) : TreeNode() {
+
+    override fun toString(): String {
+        return "(" + applyTo.toString() + ")" + operation
+    }
+
+}

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

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.tree.nodes
+
+import org.nwapw.abacus.tree.Reducer
+
+/**
+ * A tree node that holds a placeholder variable.
+ *
+ * This node holds a variable string, and acts similarly to a number,
+ * with the key difference of not actually holding a value at runtime.
+ *
+ * @param variable the actual variable name that this node represents.
+ */
+class VariableNode(val variable: String) : TreeNode() {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T {
+        return reducer.reduceNode(this)
+    }
+
+    override fun toString(): String {
+        return variable
+    }
+
+}

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

@@ -0,0 +1,109 @@
+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.exception.DomainException;
+import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.plugin.standard.StandardPlugin;
+import org.nwapw.abacus.tree.nodes.TreeNode;
+
+public class CalculationTests {
+
+    private static Abacus abacus = new Abacus(new Configuration( "precise", new String[]{}));
+
+    @BeforeClass
+    public static void prepareTests() {
+        abacus.getPluginManager().addInstantiated(new StandardPlugin(abacus.getPluginManager()));
+        abacus.reload();
+    }
+
+    private void testOutput(String input, String parseOutput, String output) {
+        TreeNode parsedTree = abacus.parseString(input);
+        Assert.assertEquals(parsedTree.toString(), parseOutput);
+        NumberInterface result = abacus.evaluateTree(parsedTree).getValue();
+        Assert.assertNotNull(result);
+        Assert.assertTrue(result.toString().startsWith(output));
+    }
+
+    private void testDomainException(String input, String parseOutput) {
+        TreeNode parsedTree = abacus.parseString(input);
+        Assert.assertEquals(parsedTree.toString(), parseOutput);
+        try {
+            abacus.evaluateTree(parsedTree);
+            Assert.fail("Function did not throw DomainException.");
+        } catch (DomainException e){ }
+    }
+
+    @Test
+    public void testAddition() {
+        testOutput("9.5+10", "(9.5+10)", "19.5");
+    }
+
+    @Test
+    public void testSubtraction() {
+        testOutput("9.5-10", "(9.5-10)", "-0.5");
+    }
+
+    @Test
+    public void testMultiplication() {
+        testOutput("9.5*10", "(9.5*10)", "95");
+    }
+
+    @Test
+    public void testDivision() {
+        testOutput("9.5/2", "(9.5/2)", "4.75");
+    }
+
+    @Test
+    public void testNegation() {
+        testOutput("-9.5", "(9.5)`", "-9.5");
+    }
+
+    @Test
+    public void testFactorial() {
+        testOutput("7!", "(7)!", "5040");
+    }
+
+    @Test
+    public void testAbs() {
+        testOutput("abs(-1)", "abs((1)`)", "1");
+        testOutput("abs(1)", "abs(1)", "1");
+    }
+
+    @Test
+    public void testLn() {
+        testDomainException("ln(-1)", "ln((1)`)");
+        testOutput("ln2", "ln(2)", "0.6931471805599453094172321214581765680755");
+    }
+
+    @Test
+    public void testSqrt() {
+        testOutput("sqrt0", "sqrt(0)", "0");
+        testOutput("sqrt4", "sqrt(4)", "2");
+        testOutput("sqrt2", "sqrt(2)", "1.4142135623730950488016887242096980785696");
+    }
+
+    @Test
+    public void testExp() {
+        testOutput("exp0", "exp(0)", "1");
+        testOutput("exp1", "exp(1)", "2.718281828459045235360287471352662497757247");
+        testOutput("exp300", "exp(300)", "1.9424263952412559365842088360176992193662086");
+        testOutput("exp(-500)", "exp((500)`)", "7.1245764067412855315491573771227552469277568");
+    }
+
+    @Test
+    public void testPow() {
+        testOutput("0^2", "(0^2)", "0");
+        testOutput("2^0", "(2^0)", "1");
+        testOutput("2^1", "(2^1)", "2");
+        testOutput("2^-1", "(2^(1)`)", "0.5");
+        testOutput("2^50", "(2^50)", "112589990684262");
+        testOutput("7^(-sqrt2*17)", "(7^((sqrt(2)*17))`)", "4.81354609155297814551845300063563");
+        testDomainException("0^0", "(0^0)");
+        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.range.NumberRange;
+import org.nwapw.abacus.number.standard.NaiveNumber;
+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

@@ -1,43 +1,69 @@
 package org.nwapw.abacus.tests;
 
+import org.jetbrains.annotations.NotNull;
 import org.junit.Assert;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import org.nwapw.abacus.Abacus;
-import org.nwapw.abacus.function.Function;
-import org.nwapw.abacus.function.Operator;
+import org.nwapw.abacus.config.Configuration;
+import org.nwapw.abacus.context.MutableEvaluationContext;
+import org.nwapw.abacus.context.PluginEvaluationContext;
 import org.nwapw.abacus.function.OperatorAssociativity;
 import org.nwapw.abacus.function.OperatorType;
-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.parsing.standard.TokenType;
 import org.nwapw.abacus.plugin.Plugin;
-import org.nwapw.abacus.tree.TokenType;
 
 import java.util.List;
 
 public class TokenizerTests {
 
-    private static Abacus abacus = new Abacus();
+    private static Abacus abacus = new Abacus(new Configuration("precise", new String[]{}));
     private static LexerTokenizer lexerTokenizer = new LexerTokenizer();
-    private static Function subtractFunction = new Function() {
+    private static NumberFunction subtractFunction = new NumberFunction() {
         @Override
-        protected boolean matchesParams(NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 2;
         }
 
         @Override
-        protected NumberInterface applyInternal(NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return params[0].subtract(params[1]);
         }
     };
     private static Plugin testPlugin = new Plugin(abacus.getPluginManager()) {
         @Override
         public void onEnable() {
-            registerOperator("+", new Operator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX,
-                    0, subtractFunction));
-            registerOperator("-", new Operator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX,
-                    0, subtractFunction));
+            registerOperator("+", new NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX,
+                    0) {
+
+                @Override
+                public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
+                    return true;
+                }
+
+                @Override
+                public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
+                    return subtractFunction.apply(context, params);
+                }
+            });
+            registerOperator("-", new NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX,
+                    0) {
+
+                @Override
+                public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
+                    return true;
+                }
+
+                @Override
+                public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
+                    return subtractFunction.apply(context, params);
+                }
+            });
             registerFunction("subtract", subtractFunction);
         }
 
@@ -59,7 +85,7 @@ public class TokenizerTests {
     public static void prepareTests() {
         abacus.getPluginManager().addListener(lexerTokenizer);
         abacus.getPluginManager().addInstantiated(testPlugin);
-        abacus.getPluginManager().load();
+        abacus.reload();
     }
 
     @Test

docs/404.html

@@ -0,0 +1,7 @@
+---
+layout: base 
+---
+<h1>404</h1>
+
+<p><strong>Page not found :(</strong></p>
+<p>The requested page could not be found.</p>

docs/Gemfile

@@ -0,0 +1,27 @@
+source "https://rubygems.org"
+
+# Hello! This is where you manage which Jekyll version is used to run.
+# When you want to use a different version, change it below, save the
+# file and run `bundle install`. Run Jekyll with `bundle exec`, like so:
+#
+#     bundle exec jekyll serve
+#
+# This will help ensure the proper Jekyll version is running.
+# Happy Jekylling!
+gem "jekyll", "3.5.2"
+
+# This is the default theme for new Jekyll sites. You may change this to anything you like.
+gem "minima", "~> 2.0"
+
+# If you want to use GitHub Pages, remove the "gem "jekyll"" above and
+# uncomment the line below. To upgrade, run `bundle update github-pages`.
+# gem "github-pages", group: :jekyll_plugins
+
+# If you have any plugins, put them here!
+group :jekyll_plugins do
+   gem "jekyll-feed", "~> 0.6"
+end
+
+# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
+gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
+

docs/Gemfile.lock

@@ -0,0 +1,58 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    addressable (2.5.1)
+      public_suffix (~> 2.0, >= 2.0.2)
+    colorator (1.1.0)
+    ffi (1.9.18)
+    forwardable-extended (2.6.0)
+    jekyll (3.5.2)
+      addressable (~> 2.4)
+      colorator (~> 1.0)
+      jekyll-sass-converter (~> 1.0)
+      jekyll-watch (~> 1.1)
+      kramdown (~> 1.3)
+      liquid (~> 4.0)
+      mercenary (~> 0.3.3)
+      pathutil (~> 0.9)
+      rouge (~> 1.7)
+      safe_yaml (~> 1.0)
+    jekyll-feed (0.9.2)
+      jekyll (~> 3.3)
+    jekyll-sass-converter (1.5.0)
+      sass (~> 3.4)
+    jekyll-watch (1.5.0)
+      listen (~> 3.0, < 3.1)
+    kramdown (1.14.0)
+    liquid (4.0.0)
+    listen (3.0.8)
+      rb-fsevent (~> 0.9, >= 0.9.4)
+      rb-inotify (~> 0.9, >= 0.9.7)
+    mercenary (0.3.6)
+    minima (2.1.1)
+      jekyll (~> 3.3)
+    pathutil (0.14.0)
+      forwardable-extended (~> 2.6)
+    public_suffix (2.0.5)
+    rb-fsevent (0.10.2)
+    rb-inotify (0.9.10)
+      ffi (>= 0.5.0, < 2)
+    rouge (1.11.1)
+    safe_yaml (1.0.4)
+    sass (3.5.1)
+      sass-listen (~> 4.0.0)
+    sass-listen (4.0.0)
+      rb-fsevent (~> 0.9, >= 0.9.4)
+      rb-inotify (~> 0.9, >= 0.9.7)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  jekyll (= 3.5.2)
+  jekyll-feed (~> 0.6)
+  minima (~> 2.0)
+  tzinfo-data
+
+BUNDLED WITH
+   1.15.3

docs/_config.yml

@@ -0,0 +1,43 @@
+# Welcome to Jekyll!
+#
+# This config file is meant for settings that affect your whole blog, values
+# which you are expected to set up once and rarely edit after that. If you find
+# yourself editing this file very often, consider using Jekyll's data files
+# feature for the data you need to update frequently.
+#
+# For technical reasons, this file is *NOT* reloaded automatically when you use
+# 'bundle exec jekyll serve'. If you change this file, please restart the server process.
+
+# Site settings
+# These are used to personalize your new site. If you look in the HTML files,
+# you will see them accessed via {{ site.title }}, {{ site.email }}, and so on.
+# You can create any custom variable you would like, and they will be accessible
+# in the templates via {{ site.myvariable }}.
+title: Abacus
+email: danila.fedorin@gmail.com
+description: > # this means to ignore newlines until "baseurl:"
+  This is the home page of Abacus,
+  a calculator developed during
+  the summer of 2017 as a tool
+  for the more tech-savvy users.
+baseurl: "/abacus" # the subpath of your site, e.g. /blog
+url: "htts://danilafe.github.io" # the base hostname & protocol for your site, e.g. http://example.com
+github_username: DanilaFe 
+include: ['_pages']
+
+# Build settings
+markdown: kramdown
+plugins:
+  - jekyll-feed
+
+# Exclude from processing.
+# The following items will not be processed, by default. Create a custom list
+# to override the default setting.
+# exclude:
+#   - Gemfile
+#   - Gemfile.lock
+#   - node_modules
+#   - vendor/bundle/
+#   - vendor/cache/
+#   - vendor/gems/
+#   - vendor/ruby/

docs/_includes/head.html

@@ -0,0 +1,17 @@
+<head>
+  <meta charset="utf-8">
+  <meta http-equiv="X-UA-Compatible" content="IE=edge">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+
+  <title>{% if page.title %}{{ page.title | escape }}{% else %}{{ site.title | escape }}{% endif %}</title>
+  <meta name="description" content="{{ page.excerpt | default: site.description | strip_html | normalize_whitespace | truncate: 160 | escape }}">
+
+  <link rel="stylesheet" href="{{ "assets/css/main.css" | relative_url }}">
+  <link rel="canonical" href="{{ page.url | replace:'index.html','' | absolute_url }}">
+  <link rel="alternate" type="application/rss+xml" title="{{ site.title | escape }}" href="{{ "/feed.xml" | relative_url }}">
+  
+  {% if jekyll.environment == 'production' and site.google_analytics %}
+  {% include google-analytics.html %}
+  {% endif %}
+</head>
+

docs/_includes/header.html

@@ -0,0 +1,10 @@
+<nav>
+  <div class="center">
+    <a href="{{ "/" | relative_url }}" class="primary-link">{{ site.title }}</a>
+    {% for page in site.pages %}
+    {% if page.in_header %}
+    <a href="{{ page.url | relative_url }}">{{ page.title }}</a>
+    {% endif %}
+    {% endfor %}
+  </div>
+</nav>

docs/_layouts/base.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+
+  {% include head.html %}
+
+  <body>
+    {% include header.html %}
+
+    <div class="content center">
+      {{ content }}
+    </div>
+
+    {% include footer.html %}
+  </body>
+
+
+</html>

docs/_layouts/home.html

@@ -0,0 +1,159 @@
+<!DOCTYPE html>
+<html>
+  {% include head.html %}
+  <style>
+  body {
+    margin: 0px;
+    margin-top: 50px;
+    color: white;
+    text-align: center;
+  }
+  h1, h2, h3, h4, h5, h6 {
+    font-family: "Source Code Pro"
+  }
+
+  img#logo {
+    margin: auto;
+    width: 100%;
+    max-width: 100px;
+  }
+
+  img#image_preview {
+    margin: auto;
+    width: 100%;
+    max-width: 432px;
+  }
+
+  div#buttons {
+    margin-top: 40px;
+    margin-bottom: 40px;
+  }
+
+  a {
+    background-color: white;
+    color: #06e8a4;
+  }
+
+  a:hover {
+    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">
+  <h1>Abacus</h1>
+  <h2>The programmer's calculator</h2>
+  <div id="buttons">
+    <a class="button inverted" href="{{ "/download" | relative_url }}">Download</a>
+    <a class="button inverted" href="{{ "/about" | relative_url }}">About</a>
+    <a class="button inverted" href="https://github.com/DanilaFe/abacus">Contribute</a>
+    <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/_layouts/page.html

@@ -0,0 +1,5 @@
+---
+layout: base
+---
+<h1>{{ page.title }}</h1>
+{{ content }}

docs/_pages/about.md

@@ -0,0 +1,27 @@
+---
+in_header: true
+layout: page
+title: About
+permalink: /about/
+---
+
+## So... what IS Abacus?
+It's a calculator. Obviously. But what makes it better than
+what already exists? There's a few things. Abacus is:
+* Programmable, and not in TI Basic.
+* Precise. With the "precise" option, Abacus can keep up to 50 significant figures.
+* Capable. Ever wonder what 2<sup>700</sup> is? How about 8!!? Abacus can tell you!
+* Offline. While Wolfram Alpha can do powerful math, it needs internet connection!
+* Built for the desktop. Why use buttons on the screen when there's buttons on the keyboard?
+* Open source. Don't like something? Help is always welcome!
+
+## Why was Abacus made?
+The initial project was proposed for the [Northwest Advanced Programming Workshop](http://nwapw.org/about/).
+You can read the project proposal on the main GitHub page, although the idea has
+changed quite a bit, mostly in shifting from "fast" to "precise".
+
+## What is Abacus made with?
+Java and Kotlin. Java provides a good layer of abstraction and a great standard
+library, while Kotlin allows for the reduction of boilerplate code and null
+safety. Using JVM-based languages also allows Abacus to expose its entire
+API to plugins, and load them at runtime.