Split the project into separate modules.

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

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

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

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

core/src/main/java/org/nwapw/abacus/function/DocumentationType.java

@@ -0,0 +1,7 @@
+package org.nwapw.abacus.function;
+
+public enum DocumentationType {
+
+    FUNCTION
+
+}

core/src/main/java/org/nwapw/abacus/function/Function.java

@@ -0,0 +1,39 @@
+package org.nwapw.abacus.function;
+
+import org.nwapw.abacus.number.NumberInterface;
+
+/**
+ * A function that operates on one or more
+ * inputs and returns a single number.
+ */
+public abstract class Function {
+
+    /**
+     * Checks whether the given params will work for the given function.
+     *
+     * @param params the given params
+     * @return true if the params can be used with this function.
+     */
+    protected abstract boolean matchesParams(NumberInterface[] params);
+
+    /**
+     * Internal apply implementation, which already receives appropriately promoted
+     * parameters that have bee run through matchesParams
+     *
+     * @param params the promoted parameters.
+     * @return the return value of the function.
+     */
+    protected abstract NumberInterface applyInternal(NumberInterface[] params);
+
+    /**
+     * Function to check, promote arguments and run the function.
+     *
+     * @param params the raw input parameters.
+     * @return the return value of the function, or null if an error occurred.
+     */
+    public NumberInterface apply(NumberInterface... params) {
+        if (!matchesParams(params)) return null;
+        return applyInternal(params);
+    }
+
+}

core/src/main/java/org/nwapw/abacus/function/OperatorAssociativity.java

@@ -0,0 +1,8 @@
+package org.nwapw.abacus.function;
+
+/**
+ * Enum to represent the associativity of an operator.
+ */
+public enum OperatorAssociativity {
+    LEFT, RIGHT
+}

core/src/main/java/org/nwapw/abacus/function/OperatorType.java

@@ -0,0 +1,8 @@
+package org.nwapw.abacus.function;
+
+/**
+ * The type of an operator, describing how it should behave.
+ */
+public enum OperatorType {
+    BINARY_INFIX, UNARY_POSTFIX, UNARY_PREFIX
+}

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

@@ -0,0 +1,151 @@
+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 java.util.*;
+
+/**
+ * A lexer that can generate tokens of a given type given a list of regular expressions
+ * to operate on.
+ *
+ * @param <T> the type used to identify which match belongs to which pattern.
+ */
+public class Lexer<T> {
+
+    /**
+     * The registered patterns.
+     */
+    private Map<PatternEntry<T>, Pattern<T>> patterns;
+
+    /**
+     * Creates a new lexer with no registered patterns.
+     */
+    public Lexer() {
+        patterns = new HashMap<>();
+    }
+
+    /**
+     * Registers a single pattern.
+     *
+     * @param pattern the pattern regex
+     * @param id      the ID by which to identify the pattern.
+     */
+    public void register(String pattern, T id) {
+        Pattern<T> compiledPattern = new Pattern<>(pattern, id);
+        if (compiledPattern.getHead() != null) patterns.put(new PatternEntry<>(pattern, id), compiledPattern);
+    }
+
+    /**
+     * Unregisters a pattern.
+     *
+     * @param pattern the pattern to unregister
+     * @param id      the ID by which to identify the pattern.
+     */
+    public void unregister(String pattern, T id) {
+        patterns.remove(new PatternEntry<>(pattern, id));
+    }
+
+    /**
+     * Reads one token from the given string.
+     *
+     * @param from    the string to read from
+     * @param startAt the index to start at
+     * @param compare the comparator used to sort tokens by their ID.
+     * @return the best match.
+     */
+    public Match<T> lexOne(String from, int startAt, Comparator<T> compare) {
+        ArrayList<Match<T>> matches = new ArrayList<>();
+        HashSet<PatternNode<T>> currentSet = new HashSet<>();
+        HashSet<PatternNode<T>> futureSet = new HashSet<>();
+        int index = startAt;
+        for (Pattern<T> pattern : patterns.values()) {
+            pattern.getHead().addInto(currentSet);
+        }
+        while (!currentSet.isEmpty()) {
+            for (PatternNode<T> node : currentSet) {
+                if (index < from.length() && node.matches(from.charAt(index))) {
+                    node.addOutputsInto(futureSet);
+                } else if (node instanceof EndNode) {
+                    matches.add(new Match<>(from.substring(startAt, index), ((EndNode<T>) node).getPatternId()));
+                }
+            }
+
+            HashSet<PatternNode<T>> tmp = currentSet;
+            currentSet = futureSet;
+            futureSet = tmp;
+            futureSet.clear();
+
+            index++;
+        }
+        matches.sort((a, b) -> compare.compare(a.getType(), b.getType()));
+        if (compare != null) {
+            matches.sort(Comparator.comparingInt(a -> a.getContent().length()));
+        }
+        return matches.isEmpty() ? null : matches.get(matches.size() - 1);
+    }
+
+    /**
+     * Reads all tokens from a string.
+     *
+     * @param from    the string to start from.
+     * @param startAt the index to start at.
+     * @param compare the comparator used to sort matches by their IDs.
+     * @return the resulting list of matches, in order, or null on error.
+     */
+    public List<Match<T>> lexAll(String from, int startAt, Comparator<T> compare) {
+        int index = startAt;
+        ArrayList<Match<T>> matches = new ArrayList<>();
+        Match<T> lastMatch = null;
+        while (index < from.length() && (lastMatch = lexOne(from, index, compare)) != null) {
+            int length = lastMatch.getContent().length();
+            if (length == 0) return null;
+            matches.add(lastMatch);
+            index += length;
+        }
+        if (lastMatch == null) return null;
+        return matches;
+    }
+
+    /**
+     * An entry that represents a pattern that has been registered with the lexer.
+     *
+     * @param <T> the type used to identify the pattern.
+     */
+    private static class PatternEntry<T> {
+        /**
+         * The name of the entry.
+         */
+        public String name;
+        /**
+         * The id of the entry.
+         */
+        public T id;
+
+        /**
+         * Creates a new pattern entry with the given name and id.
+         *
+         * @param name the name of the pattern entry.
+         * @param id   the id of the pattern entry.
+         */
+        public PatternEntry(String name, T id) {
+            this.name = name;
+            this.id = id;
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(name, id);
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            return obj instanceof PatternEntry &&
+                    ((PatternEntry) obj).name.equals(name) &&
+                    ((PatternEntry) obj).id.equals(id);
+        }
+    }
+
+}

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

@@ -0,0 +1,15 @@
+package org.nwapw.abacus.lexing.pattern;
+
+/**
+ * A pattern node that matches any character.
+ *
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
+public class AnyNode<T> extends PatternNode<T> {
+
+    @Override
+    public boolean matches(char other) {
+        return true;
+    }
+
+}

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

@@ -0,0 +1,33 @@
+package org.nwapw.abacus.lexing.pattern;
+
+/**
+ * A node that represents a successful match.
+ *
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
+public class EndNode<T> extends PatternNode<T> {
+
+    /**
+     * The ID of the pattenr that has been matched.
+     */
+    private T patternId;
+
+    /**
+     * Creates a new end node with the given ID.
+     *
+     * @param patternId the pattern ID.
+     */
+    public EndNode(T patternId) {
+        this.patternId = patternId;
+    }
+
+    /**
+     * Gets the pattern ID.
+     *
+     * @return the pattern ID.
+     */
+    public T getPatternId() {
+        return patternId;
+    }
+
+}

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

@@ -0,0 +1,20 @@
+package org.nwapw.abacus.lexing.pattern;
+
+import java.util.Collection;
+
+/**
+ * A node that is used as structural glue in pattern compilation.
+ *
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
+public class LinkNode<T> extends PatternNode<T> {
+
+    @Override
+    public void addInto(Collection<PatternNode<T>> into) {
+        if (!into.contains(this)) {
+            into.add(this);
+            addOutputsInto(into);
+        }
+    }
+
+}

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

@@ -0,0 +1,47 @@
+package org.nwapw.abacus.lexing.pattern;
+
+/**
+ * A match that has been generated by the lexer.
+ *
+ * @param <T> the type used to represent the ID of the pattern this match belongs to.
+ */
+public class Match<T> {
+
+    /**
+     * The content of this match.
+     */
+    private String content;
+    /**
+     * The pattern type this match matched.
+     */
+    private T type;
+
+    /**
+     * Creates a new match with the given parameters.
+     *
+     * @param content the content of this match.
+     * @param type    the type of the match.
+     */
+    public Match(String content, T type) {
+        this.content = content;
+        this.type = type;
+    }
+
+    /**
+     * Gets the content of this match.
+     *
+     * @return the content.
+     */
+    public String getContent() {
+        return content;
+    }
+
+    /**
+     * Gets the pattern type of the node.
+     *
+     * @return the ID of the pattern that this match matched.
+     */
+    public T getType() {
+        return type;
+    }
+}

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

@@ -0,0 +1,268 @@
+package org.nwapw.abacus.lexing.pattern;
+
+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.
+ *
+ * @param <T> the type that is used to identify and sort this pattern.
+ */
+public class Pattern<T> {
+
+    /**
+     * The ID of this pattern.
+     */
+    private T id;
+    /**
+     * The head of this pattern.
+     */
+    private PatternNode<T> head;
+    /**
+     * The source string of this pattern.
+     */
+    private String source;
+    /**
+     * The index at which the compilation has stopped.
+     */
+    private int index;
+
+    /**
+     * 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>>>() {{
+                put('+', Pattern.this::transformPlus);
+                put('*', Pattern.this::transformStar);
+                put('?', Pattern.this::transformQuestion);
+            }};
+
+    /**
+     * Creates / compiles a new pattern with the given id from the given string.
+     *
+     * @param from the string to compile a pattern from.
+     * @param id   the ID to use.
+     */
+    public Pattern(String from, T id) {
+        this.id = id;
+        index = 0;
+        source = from;
+
+        PatternChain<T> chain = parseSegment(false);
+        if (chain == null) {
+            head = null;
+        } else {
+            chain.append(new EndNode<>(id));
+            head = chain.head;
+        }
+    }
+
+    /**
+     * Removes all characters that are considered "special" from
+     * the given string.
+     *
+     * @param from the string to sanitize.
+     * @return the resulting string.
+     */
+    public static String sanitize(String from) {
+        Pattern<Integer> pattern = new Pattern<>("", 0);
+        from = from.replace(".", "\\.");
+        from = from.replace("|", "\\|");
+        from = from.replace("(", "\\(");
+        from = from.replace(")", "\\)");
+        for (Character key : pattern.operations.keySet()) {
+            from = from.replace("" + key, "\\" + key);
+        }
+        return from;
+    }
+
+    /**
+     * A regex operator function that turns the chain
+     * into a one-or-more chain.
+     *
+     * @param chain the chain to transform.
+     * @return the modified chain.
+     */
+    private PatternChain<T> transformPlus(PatternChain<T> chain) {
+        chain.tail.outputStates.add(chain.head);
+        return chain;
+    }
+
+    /**
+     * A regex operator function that turns the chain
+     * into a zero-or-more chain.
+     *
+     * @param chain the chain to transform.
+     * @return the modified chain.
+     */
+    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);
+        chain.head = newHead;
+        chain.tail = newTail;
+        return chain;
+    }
+
+    /**
+     * A regex operator function that turns the chain
+     * into a zero-or-one chain.
+     *
+     * @param chain the chain to transform.
+     * @return the modified chain.
+     */
+    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);
+        chain.head = newHead;
+        chain.tail = newTail;
+        return chain;
+    }
+
+    /**
+     * Combines a collection of chains into one OR chain.
+     *
+     * @param collection the collection of chains to combine.
+     * @return the resulting OR chain.
+     */
+    private PatternChain<T> combineChains(Collection<PatternChain<T>> collection) {
+        LinkNode<T> head = new LinkNode<>();
+        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);
+        }
+        return newChain;
+    }
+
+    /**
+     * Parses a single value from the input into a chain.
+     *
+     * @return the resulting chain, or null on error.
+     */
+    private PatternChain<T> parseValue() {
+        if (index >= source.length()) return null;
+        if (source.charAt(index) == '\\') {
+            if (++index >= source.length()) return null;
+        }
+        return new PatternChain<>(new ValueNode<>(source.charAt(index++)));
+    }
+
+    /**
+     * Parses a [] range from the input into a chain.
+     *
+     * @return the resulting chain, or null on error.
+     */
+    private PatternChain<T> parseOr() {
+        Stack<PatternChain<T>> orStack = new Stack<>();
+        index++;
+        while (index < source.length() && source.charAt(index) != ']') {
+            if (source.charAt(index) == '-') {
+                index++;
+                if (orStack.empty() || orStack.peek().tail.range() == '\0') return null;
+                PatternChain<T> bottomRange = orStack.pop();
+                PatternChain<T> topRange = parseValue();
+                if (topRange == null || topRange.tail.range() == '\0') return null;
+
+                orStack.push(new PatternChain<>(new RangeNode<>(bottomRange.tail.range(), topRange.tail.range())));
+            } else {
+                PatternChain<T> newChain = parseValue();
+                if (newChain == null) return null;
+                orStack.push(newChain);
+            }
+        }
+        if (index++ >= source.length()) return null;
+        return (orStack.size() == 1) ? orStack.pop() : combineChains(orStack);
+    }
+
+    /**
+     * Parses a repeatable segment from the input into a chain
+     *
+     * @param isSubsegment whether the segment is a sub-expression "()", and therefore
+     *                     whether to expect a closing brace.
+     * @return the resulting chain, or null on error.
+     */
+    private PatternChain<T> parseSegment(boolean isSubsegment) {
+        if (index >= source.length() || ((source.charAt(index) != '(') && isSubsegment)) return null;
+        if (isSubsegment) index++;
+
+        Stack<PatternChain<T>> orChain = new Stack<>();
+        PatternChain<T> fullChain = new PatternChain<>();
+        PatternChain<T> currentChain = null;
+        while (index < source.length() && source.charAt(index) != ')') {
+            char currentChar = source.charAt(index);
+            if (operations.containsKey(currentChar)) {
+                if (currentChain == null) return null;
+
+                currentChain = operations.get(currentChar).apply(currentChain);
+                fullChain.append(currentChain);
+                currentChain = null;
+                index++;
+            } else if (currentChar == '|') {
+                if (currentChain == null) return null;
+
+                fullChain.append(currentChain);
+                orChain.push(fullChain);
+                currentChain = null;
+                fullChain = new PatternChain<>();
+                if (++index >= source.length()) return null;
+            } else if (currentChar == '(') {
+                if (currentChain != null) {
+                    fullChain.append(currentChain);
+                }
+
+                currentChain = parseSegment(true);
+                if (currentChain == null) return null;
+            } else if (currentChar == '[') {
+                if (currentChain != null) {
+                    fullChain.append(currentChain);
+                }
+                currentChain = parseOr();
+                if (currentChain == null) return null;
+            } else if (currentChar == '.') {
+                if (currentChain != null) {
+                    fullChain.append(currentChain);
+                }
+                currentChain = new PatternChain<>(new AnyNode<>());
+                index++;
+            } else {
+                if (currentChain != null) {
+                    fullChain.append(currentChain);
+                }
+                currentChain = parseValue();
+                if (currentChain == null) return null;
+            }
+        }
+
+        if (!(!isSubsegment || (index < source.length() && source.charAt(index) == ')'))) return null;
+        if (isSubsegment) index++;
+
+        if (currentChain != null) fullChain.append(currentChain);
+        if (!orChain.empty()) {
+            orChain.push(fullChain);
+            fullChain = combineChains(orChain);
+        }
+
+        return fullChain;
+    }
+
+    /**
+     * Gets the head PatternNode, for use in matching
+     *
+     * @return the pattern node.
+     */
+    public PatternNode<T> getHead() {
+        return head;
+    }
+}

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

@@ -0,0 +1,80 @@
+package org.nwapw.abacus.lexing.pattern;
+
+/**
+ * A chain of nodes that can be treated as a single unit.
+ * Used during pattern compilation.
+ *
+ * @param <T> the type used to identify which pattern has been matched.
+ */
+public class PatternChain<T> {
+
+    /**
+     * The head node of the chain.
+     */
+    public PatternNode<T> head;
+    /**
+     * The tail node of the chain.
+     */
+    public PatternNode<T> tail;
+
+    /**
+     * Creates a new chain with the given start and end.
+     *
+     * @param head the start of the chain.
+     * @param tail the end of the chain.
+     */
+    public PatternChain(PatternNode<T> head, PatternNode<T> tail) {
+        this.head = head;
+        this.tail = tail;
+    }
+
+    /**
+     * Creates a chain that starts and ends with the same node.
+     *
+     * @param node the node to use.
+     */
+    public PatternChain(PatternNode<T> node) {
+        this(node, node);
+    }
+
+    /**
+     * Creates an empty chain.
+     */
+    public PatternChain() {
+        this(null);
+    }
+
+    /**
+     * Appends the other chain to this one. This modifies
+     * the nodes, as well.
+     * If this chain is empty, it is set to the other.
+     *
+     * @param other the other chain to append.
+     */
+    public void append(PatternChain<T> other) {
+        if (other.head == null || tail == null) {
+            this.head = other.head;
+            this.tail = other.tail;
+        } else {
+            tail.outputStates.add(other.head);
+            tail = other.tail;
+        }
+    }
+
+    /**
+     * Appends a single node to this chain. This modifies
+     * the nodes, as well.
+     * If this chain is empty, it is set to the node.
+     *
+     * @param node the node to append to this chain.
+     */
+    public void append(PatternNode<T> node) {
+        if (tail == null) {
+            head = tail = node;
+        } else {
+            tail.outputStates.add(node);
+            tail = node;
+        }
+    }
+
+}

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

@@ -0,0 +1,68 @@
+package org.nwapw.abacus.lexing.pattern;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * A base class for a pattern node. Provides all functions
+ * necessary for matching, and is constructed by a Pattern instance
+ * from a string.
+ *
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
+public class PatternNode<T> {
+
+    /**
+     * The set of states to which the lexer should continue
+     * should this node be correctly matched.
+     */
+    protected Set<PatternNode<T>> outputStates;
+
+    /**
+     * Creates a new pattern node.
+     */
+    public PatternNode() {
+        outputStates = new HashSet<>();
+    }
+
+    /**
+     * Determines whether the current input character can
+     * be matched by this node.
+     *
+     * @param other the character being matched.
+     * @return true if the character can be matched, false otherwise.
+     */
+    public boolean matches(char other) {
+        return false;
+    }
+
+    /**
+     * If this node can be used as part of a range, returns that value.
+     *
+     * @return a NULL terminator if this character cannot be converted
+     * into a range bound, or the appropriate range bound if it can.
+     */
+    public char range() {
+        return '\0';
+    }
+
+    /**
+     * Adds this node in a collection of other nodes.
+     *
+     * @param into the collection to add into.
+     */
+    public void addInto(Collection<PatternNode<T>> into) {
+        into.add(this);
+    }
+
+    /**
+     * Adds the node's children into a collection of other nodes.
+     *
+     * @param into the collection to add into.
+     */
+    public void addOutputsInto(Collection<PatternNode<T>> into) {
+        outputStates.forEach(e -> e.addInto(into));
+    }
+
+}

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

@@ -0,0 +1,35 @@
+package org.nwapw.abacus.lexing.pattern;
+
+/**
+ * A node that matches a range of characters.
+ *
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
+public class RangeNode<T> extends PatternNode<T> {
+
+    /**
+     * The bottom bound of the range, inclusive.
+     */
+    private char from;
+    /**
+     * The top bound of the range, inclusive.
+     */
+    private char to;
+
+    /**
+     * Creates a new range node from the given range.
+     *
+     * @param from the bottom bound of the range.
+     * @param to   the top bound of hte range.
+     */
+    public RangeNode(char from, char to) {
+        this.from = from;
+        this.to = to;
+    }
+
+    @Override
+    public boolean matches(char other) {
+        return other >= from && other <= to;
+    }
+
+}

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

@@ -0,0 +1,33 @@
+package org.nwapw.abacus.lexing.pattern;
+
+/**
+ * A node that matches a single value.
+ *
+ * @param <T> the type that's used to tell which pattern this node belongs to.
+ */
+public class ValueNode<T> extends PatternNode<T> {
+
+    /**
+     * The value this node matches.
+     */
+    private char value;
+
+    /**
+     * Creates a new node that matches the given character.
+     *
+     * @param value the character value of the node.
+     */
+    public ValueNode(char value) {
+        this.value = value;
+    }
+
+    @Override
+    public boolean matches(char other) {
+        return other == value;
+    }
+
+    @Override
+    public char range() {
+        return value;
+    }
+}

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

@@ -0,0 +1,16 @@
+package org.nwapw.abacus.number;
+
+/**
+ * Exception thrown when the computation is interrupted by
+ * the user.
+ */
+public class ComputationInterruptedException extends RuntimeException {
+
+    /**
+     * Creates a new exception of this type.
+     */
+    public ComputationInterruptedException(){
+        super("Computation interrupted by user.");
+    }
+
+}

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

@@ -0,0 +1,136 @@
+package org.nwapw.abacus.number;
+
+/**
+ * An implementation of NumberInterface using a double.
+ */
+public class NaiveNumber extends NumberInterface {
+
+    /**
+     * The number zero.
+     */
+    public static final NaiveNumber ZERO = new NaiveNumber(0);
+    /**
+     * The number one.
+     */
+    public static final NaiveNumber ONE = new NaiveNumber(1);
+    /**
+     * The value of this number.
+     */
+    private double value;
+
+    /**
+     * Creates a new NaiveNumber with the given string.
+     *
+     * @param value the value, which will be parsed as a double.
+     */
+    public NaiveNumber(String value) {
+        this(Double.parseDouble(value));
+    }
+
+    /**
+     * Creates a new NaiveNumber with the given value.
+     *
+     * @param value the value to use.
+     */
+    public NaiveNumber(double value) {
+        this.value = value;
+    }
+
+    @Override
+    public int getMaxPrecision() {
+        return 18;
+    }
+
+    @Override
+    public NumberInterface multiplyInternal(NumberInterface multiplier) {
+        return new NaiveNumber(value * ((NaiveNumber) multiplier).value);
+    }
+
+    @Override
+    public NumberInterface divideInternal(NumberInterface divisor) {
+        return new NaiveNumber(value / ((NaiveNumber) divisor).value);
+    }
+
+    @Override
+    public NumberInterface addInternal(NumberInterface summand) {
+        return new NaiveNumber(value + ((NaiveNumber) summand).value);
+    }
+
+    @Override
+    public NumberInterface subtractInternal(NumberInterface subtrahend) {
+        return new NaiveNumber(value - ((NaiveNumber) subtrahend).value);
+    }
+
+    @Override
+    public NumberInterface negateInternal() {
+        return new NaiveNumber(-value);
+    }
+
+    @Override
+    public NumberInterface intPowInternal(int exponent) {
+        if (exponent == 0) {
+            return NaiveNumber.ONE;
+        }
+        boolean takeReciprocal = exponent < 0;
+        exponent = Math.abs(exponent);
+        NumberInterface power = this;
+        for (int currentExponent = 1; currentExponent < exponent; currentExponent++) {
+            power = power.multiply(this);
+        }
+        if (takeReciprocal) {
+            power = NaiveNumber.ONE.divide(power);
+        }
+        return power;
+    }
+
+    @Override
+    public int compareTo(NumberInterface number) {
+        NaiveNumber num = (NaiveNumber) number;
+        return Double.compare(value, num.value);
+    }
+
+    @Override
+    public int signum() {
+        return this.compareTo(ZERO);
+    }
+
+    @Override
+    public NumberInterface ceilingInternal() {
+        return new NaiveNumber(Math.ceil(value));
+    }
+
+    @Override
+    public NumberInterface floorInternal() {
+        return new NaiveNumber(Math.floor(value));
+    }
+
+    @Override
+    public NumberInterface fractionalPartInternal() {
+        return new NaiveNumber(value - Math.floor(value));
+    }
+
+    @Override
+    public int intValue() {
+        return (int) value;
+    }
+
+    @Override
+    public NumberInterface promoteToInternal(Class<? extends NumberInterface> toClass) {
+        if (toClass == this.getClass()) return this;
+        else if (toClass == PreciseNumber.class) {
+            return new PreciseNumber(Double.toString(value));
+        }
+        return null;
+    }
+
+    public String toString() {
+        double shiftBy = Math.pow(10, 10);
+        return Double.toString(Math.round(value * shiftBy) / shiftBy);
+    }
+
+    @Override
+    public NumberInterface getMaxError(){
+        return new NaiveNumber(Math.pow(10, -18));
+    }
+}
+

core/src/main/java/org/nwapw/abacus/number/NumberInterface.java

@@ -0,0 +1,267 @@
+package org.nwapw.abacus.number;
+
+/**
+ * An interface used to represent a number.
+ */
+public abstract class NumberInterface {
+
+    /**
+     * Check if the thread was interrupted and
+     * throw an exception to end the computation.
+     */
+    private static void checkInterrupted(){
+        if(Thread.currentThread().isInterrupted())
+            throw new ComputationInterruptedException();
+    }
+    /**
+     * The maximum precision to which this number operates.
+     *
+     * @return the precision.
+     */
+    public abstract int getMaxPrecision();
+
+    /**
+     * Multiplies this number by another, returning
+     * a new number instance.
+     *
+     * @param multiplier the multiplier
+     * @return the result of the multiplication.
+     */
+    protected abstract NumberInterface multiplyInternal(NumberInterface multiplier);
+
+    /**
+     * 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.
+     */
+    public final NumberInterface multiply(NumberInterface multiplier){
+        checkInterrupted();
+        return multiplyInternal(multiplier);
+    }
+
+    /**
+     * Divides this number by another, returning
+     * a new number instance.
+     *
+     * @param divisor the divisor
+     * @return the result of the division.
+     */
+    protected abstract NumberInterface divideInternal(NumberInterface divisor);
+
+    /**
+     * 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.
+     */
+    public final NumberInterface divide(NumberInterface divisor){
+        checkInterrupted();
+        return divideInternal(divisor);
+    }
+
+    /**
+     * Adds this number to another, returning
+     * a new number instance.
+     *
+     * @param summand the summand
+     * @return the result of the summation.
+     */
+    protected abstract NumberInterface addInternal(NumberInterface summand);
+
+    /**
+     * 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.
+     */
+    public final NumberInterface add(NumberInterface summand){
+        checkInterrupted();
+        return addInternal(summand);
+    }
+
+    /**
+     * Subtracts another number from this number,
+     * a new number instance.
+     *
+     * @param subtrahend the subtrahend.
+     * @return the result of the subtraction.
+     */
+    protected abstract NumberInterface subtractInternal(NumberInterface subtrahend);
+
+    /**
+     * 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.
+     */
+    public final NumberInterface subtract(NumberInterface subtrahend){
+        checkInterrupted();
+        return subtractInternal(subtrahend);
+    }
+
+    /**
+     * Returns a new instance of this number with
+     * the sign flipped.
+     *
+     * @return the new instance.
+     */
+    protected abstract NumberInterface negateInternal();
+
+
+    /**
+     * 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.
+     */
+    public final NumberInterface negate(){
+        checkInterrupted();
+        return negateInternal();
+    }
+
+    /**
+     * Raises this number to an integer power.
+     *
+     * @param exponent the exponent to which to take the number.
+     * @return the resulting value.
+     */
+    protected abstract NumberInterface intPowInternal(int exponent);
+
+    /**
+     * 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.
+     */
+    public final NumberInterface intPow(int exponent){
+        checkInterrupted();
+        return intPowInternal(exponent);
+    }
+
+    /**
+     * Compares this number to another.
+     *
+     * @param number the number to compare to.
+     * @return same as Integer.compare();
+     */
+    public abstract int compareTo(NumberInterface number);
+
+    /**
+     * Same as Math.signum().
+     *
+     * @return 1 if this number is positive, -1 if this number is negative, 0 if this number is 0.
+     */
+    public abstract int signum();
+
+    /**
+     * 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.
+     */
+    protected abstract NumberInterface ceilingInternal();
+
+    /**
+     * 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.
+     */
+    public final NumberInterface ceiling(){
+        checkInterrupted();
+        return ceilingInternal();
+    }
+
+    /**
+     * Return the greatest integer less than or equal to the number.
+     *
+     * @return the greatest integer smaller or equal the number.
+     */
+    protected abstract NumberInterface floorInternal();
+
+    /**
+     * 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.
+     */
+    public final NumberInterface floor(){
+        checkInterrupted();
+        return floorInternal();
+    }
+
+    /**
+     * Returns the fractional part of the number.
+     *
+     * @return the fractional part of the number.
+     */
+    protected abstract NumberInterface fractionalPartInternal();
+
+    /**
+     * 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.
+     */
+    public final NumberInterface fractionalPart(){
+        checkInterrupted();
+        return fractionalPartInternal();
+    }
+
+    /**
+     * Returns the integer representation of this number, discarding any fractional part,
+     * if int can hold the value.
+     *
+     * @return the integer value of this number.
+     */
+    public abstract int intValue();
+
+    /**
+     * Promotes this class to another number class.
+     *
+     * @param toClass the class to promote to.
+     * @return the resulting new instance.
+     */
+    @Deprecated
+    protected abstract NumberInterface promoteToInternal(Class<? extends NumberInterface> toClass);
+
+    /**
+     * Promotes this class to another number class. Also, checks if the
+     * thread has been interrupted, and if so, throws
+     * an exception.
+     *
+     * @param toClass the class to promote to.
+     * @return the resulting new instance.
+     */
+    @Deprecated
+    public final NumberInterface promoteTo(Class<? extends NumberInterface> toClass) {
+        checkInterrupted();
+        return promoteToInternal(toClass);
+    }
+
+    /**
+     * Returns the smallest error this instance can tolerate depending
+     * on its precision and value.
+     * @return the smallest error that should be permitted in calculations.
+     */
+    public abstract NumberInterface getMaxError();
+
+}

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

@@ -0,0 +1,172 @@
+package org.nwapw.abacus.number;
+
+import java.math.BigDecimal;
+import java.math.MathContext;
+
+/**
+ * A number that uses a BigDecimal to store its value,
+ * leading to infinite possible precision.
+ */
+public class PreciseNumber extends NumberInterface {
+
+    /**
+     * The number one.
+     */
+    public static final PreciseNumber ONE = new PreciseNumber(BigDecimal.ONE);
+    /**
+     * The number zero.
+     */
+    public static final PreciseNumber ZERO = new PreciseNumber(BigDecimal.ZERO);
+    /**
+     * The number ten.
+     */
+    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.
+     */
+    BigDecimal value;
+
+    /**
+     * Constructs a precise number from the given string.
+     *
+     * @param string a string representation of the number meeting the same conditions
+     *               as the BidDecimal(String) constructor.
+     */
+    public PreciseNumber(String string) {
+        value = new BigDecimal(string);
+    }
+
+    /**
+     * Constructs a precise number from the given BigDecimal.
+     *
+     * @param value a BigDecimal object representing the value of the number.
+     */
+    public PreciseNumber(BigDecimal value) {
+        this.value = value;
+    }
+
+    @Override
+    public int getMaxPrecision() {
+        return internalContext.getPrecision();
+    }
+
+    @Override
+    public NumberInterface multiplyInternal(NumberInterface multiplier) {
+        return new PreciseNumber(this.value.multiply(((PreciseNumber) multiplier).value));
+    }
+
+    @Override
+    public NumberInterface divideInternal(NumberInterface divisor) {
+        return new PreciseNumber(value.divide(((PreciseNumber) divisor).value, internalContext));
+    }
+
+    @Override
+    public NumberInterface addInternal(NumberInterface summand) {
+        return new PreciseNumber(value.add(((PreciseNumber) summand).value));
+    }
+
+    @Override
+    public NumberInterface subtractInternal(NumberInterface subtrahend) {
+        return new PreciseNumber(value.subtract(((PreciseNumber) subtrahend).value));
+    }
+
+    @Override
+    public NumberInterface intPowInternal(int exponent) {
+        if (exponent == 0) {
+            return PreciseNumber.ONE;
+        }
+        boolean takeReciprocal = exponent < 0;
+        exponent = Math.abs(exponent);
+        NumberInterface power = this;
+        for (int currentExponent = 1; currentExponent < exponent; currentExponent++) {
+            power = power.multiply(this);
+        }
+        if (takeReciprocal) {
+            power = PreciseNumber.ONE.divide(power);
+        }
+        return power;
+    }
+
+    @Override
+    public int compareTo(NumberInterface number) {
+        return value.compareTo(((PreciseNumber) number).value);
+    }
+
+    @Override
+    public int signum() {
+        return value.signum();
+    }
+
+    @Override
+    public NumberInterface ceilingInternal() {
+        String str = value.toPlainString();
+        int decimalIndex = str.indexOf('.');
+        if (decimalIndex != -1) {
+            return this.floor().add(ONE);
+        }
+        return this;
+    }
+
+    @Override
+    public NumberInterface floorInternal() {
+        String str = value.toPlainString();
+        int decimalIndex = str.indexOf('.');
+        if (decimalIndex != -1) {
+            NumberInterface floor = new PreciseNumber(str.substring(0, decimalIndex));
+            if(signum() == -1){
+                floor = floor.subtract(ONE);
+            }
+            return floor;
+        }
+        return this;
+    }
+
+    @Override
+    public NumberInterface fractionalPartInternal() {
+        return this.subtractInternal(floorInternal());
+    }
+
+    @Override
+    public int intValue() {
+        return value.intValue();
+    }
+
+    @Override
+    public NumberInterface negateInternal() {
+        return new PreciseNumber(value.negate());
+    }
+
+    @Override
+    public NumberInterface promoteToInternal(Class<? extends NumberInterface> toClass) {
+        if (toClass == this.getClass()) {
+            return this;
+        }
+        return null;
+    }
+
+    @Override
+    public String toString() {
+        return value.round(outputContext).toString();
+    }
+
+    @Override
+    public NumberInterface getMaxError(){
+        return new PreciseNumber(value.ulp()).multiplyInternal(TEN.intPowInternal(value.precision()-internalContext.getPrecision()));
+    }
+}

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

@@ -0,0 +1,67 @@
+package org.nwapw.abacus.parsing;
+
+import org.nwapw.abacus.lexing.Lexer;
+import org.nwapw.abacus.lexing.pattern.Match;
+import org.nwapw.abacus.lexing.pattern.Pattern;
+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;
+
+/**
+ * A tokenzier that uses the lexer class and registered function and operator
+ * names to turn input into tokens in O(n) time.
+ */
+public class LexerTokenizer implements Tokenizer<Match<TokenType>>, PluginListener {
+
+    /**
+     * Comparator used to sort the tokens produced by the lexer.
+     */
+    protected static final Comparator<TokenType> TOKEN_SORTER = Comparator.comparingInt(e -> e.priority);
+
+    /**
+     * The lexer instance used to turn strings into matches.
+     */
+    private Lexer<TokenType> lexer;
+
+    /**
+     * Creates a new lexer tokenizer.
+     */
+    public LexerTokenizer() {
+        lexer = new Lexer<TokenType>() {{
+            register(" ", TokenType.WHITESPACE);
+            register(",", TokenType.COMMA);
+            register("[0-9]*(\\.[0-9]+)?", TokenType.NUM);
+            register("\\(", TokenType.OPEN_PARENTH);
+            register("\\)", TokenType.CLOSE_PARENTH);
+        }};
+    }
+
+    @Override
+    public List<Match<TokenType>> tokenizeString(String string) {
+        return lexer.lexAll(string, 0, TOKEN_SORTER);
+    }
+
+    @Override
+    public void onLoad(PluginManager manager) {
+        for (String operator : manager.getAllOperators()) {
+            lexer.register(Pattern.sanitize(operator), TokenType.OP);
+        }
+        for (String function : manager.getAllFunctions()) {
+            lexer.register(Pattern.sanitize(function), TokenType.FUNCTION);
+        }
+    }
+
+    @Override
+    public void onUnload(PluginManager manager) {
+        for (String operator : manager.getAllOperators()) {
+            lexer.unregister(Pattern.sanitize(operator), TokenType.OP);
+        }
+        for (String function : manager.getAllFunctions()) {
+            lexer.unregister(Pattern.sanitize(function), TokenType.FUNCTION);
+        }
+    }
+
+}

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

@@ -0,0 +1,22 @@
+package org.nwapw.abacus.parsing;
+
+import org.nwapw.abacus.tree.TreeNode;
+
+import java.util.List;
+
+/**
+ * An itnerface 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> {
+
+    /**
+     * Constructs a tree out of the given tokens.
+     *
+     * @param tokens the tokens to construct a tree from.
+     * @return the constructed tree, or null on error.
+     */
+    public TreeNode constructTree(List<T> tokens);
+}

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

@@ -0,0 +1,187 @@
+package org.nwapw.abacus.parsing;
+
+import org.nwapw.abacus.Abacus;
+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.plugin.PluginListener;
+import org.nwapw.abacus.plugin.PluginManager;
+import org.nwapw.abacus.tree.*;
+
+import java.util.*;
+
+/**
+ * A parser that uses shunting yard to rearranged matches into postfix
+ * and then convert them into a parse tree.
+ */
+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.
+     */
+    private Map<String, Integer> precedenceMap;
+    /**
+     * Map of operator associativity, loaded from the plugin operators.
+     */
+    private Map<String, OperatorAssociativity> associativityMap;
+    /**
+     * Map of operator types, loaded from plugin operators.
+     */
+    private Map<String, OperatorType> typeMap;
+
+    /**
+     * Creates a new Shunting Yard parser with the given Abacus instance.
+     *
+     * @param abacus the abacus instance.
+     */
+    public ShuntingYardParser(Abacus abacus) {
+        this.abacus = abacus;
+        precedenceMap = new HashMap<>();
+        associativityMap = new HashMap<>();
+        typeMap = new HashMap<>();
+    }
+
+    /**
+     * Rearranges tokens into a postfix list, using Shunting Yard.
+     *
+     * @param from the tokens to be rearranged.
+     * @return the resulting list of rearranged tokens.
+     */
+    public List<Match<TokenType>> intoPostfix(List<Match<TokenType>> from) {
+        ArrayList<Match<TokenType>> output = new ArrayList<>();
+        Stack<Match<TokenType>> tokenStack = new Stack<>();
+        TokenType previousType;
+        TokenType matchType = null;
+        while (!from.isEmpty()) {
+            Match<TokenType> match = from.remove(0);
+            previousType = matchType;
+            matchType = match.getType();
+            if (matchType == TokenType.NUM) {
+                output.add(match);
+            } else if (matchType == TokenType.FUNCTION) {
+                output.add(new Match<>("", TokenType.INTERNAL_FUNCTION_END));
+                tokenStack.push(match);
+            } else if (matchType == TokenType.OP) {
+                String tokenString = match.getContent();
+                OperatorType type = typeMap.get(tokenString);
+                int precedence = precedenceMap.get(tokenString);
+                OperatorAssociativity associativity = associativityMap.get(tokenString);
+
+                if (type == OperatorType.UNARY_POSTFIX) {
+                    output.add(match);
+                    continue;
+                }
+
+                if (tokenString.equals("-") && (previousType == null || previousType == TokenType.OP ||
+                        previousType == TokenType.OPEN_PARENTH)) {
+                    from.add(0, new Match<>("`", TokenType.OP));
+                    continue;
+                }
+
+                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) {
+                        int otherPrecedence = precedenceMap.get(otherMatch.getContent());
+                        if (otherPrecedence < precedence ||
+                                (associativity == OperatorAssociativity.RIGHT && otherPrecedence == precedence)) {
+                            break;
+                        }
+                    }
+                    output.add(tokenStack.pop());
+                }
+                tokenStack.push(match);
+            } else if (matchType == TokenType.OPEN_PARENTH) {
+                tokenStack.push(match);
+            } else if (matchType == TokenType.CLOSE_PARENTH || matchType == TokenType.COMMA) {
+                while (!tokenStack.empty() && tokenStack.peek().getType() != TokenType.OPEN_PARENTH) {
+                    output.add(tokenStack.pop());
+                }
+                if (tokenStack.empty()) return null;
+                if (matchType == TokenType.CLOSE_PARENTH) {
+                    tokenStack.pop();
+                }
+            }
+        }
+        while (!tokenStack.empty()) {
+            Match<TokenType> match = tokenStack.peek();
+            TokenType newMatchType = match.getType();
+            if (!(newMatchType == TokenType.OP || newMatchType == TokenType.FUNCTION)) return null;
+            output.add(tokenStack.pop());
+        }
+        return output;
+    }
+
+    /**
+     * Constructs a tree recursively from a list of tokens.
+     *
+     * @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;
+        Match<TokenType> match = matches.remove(0);
+        TokenType matchType = match.getType();
+        if (matchType == TokenType.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);
+            } else {
+                TreeNode applyTo = constructRecursive(matches);
+                if (applyTo == null) return null;
+                else return new UnaryNode(operator, applyTo);
+            }
+        } else if (matchType == TokenType.NUM) {
+            return new NumberNode(abacus.numberFromString(match.getContent()));
+        } else if (matchType == TokenType.FUNCTION) {
+            String functionName = match.getContent();
+            FunctionNode node = new FunctionNode(functionName);
+            while (!matches.isEmpty() && matches.get(0).getType() != TokenType.INTERNAL_FUNCTION_END) {
+                TreeNode argument = constructRecursive(matches);
+                if (argument == null) return null;
+                node.prependChild(argument);
+            }
+            if (matches.isEmpty()) return null;
+            matches.remove(0);
+            return node;
+        }
+        return null;
+    }
+
+    @Override
+    public TreeNode constructTree(List<Match<TokenType>> tokens) {
+        tokens = intoPostfix(new ArrayList<>(tokens));
+        if(tokens == null) return null;
+        Collections.reverse(tokens);
+        TreeNode constructedTree = constructRecursive(tokens);
+        return tokens.size() == 0 ? constructedTree : null;
+    }
+
+    @Override
+    public void onLoad(PluginManager manager) {
+        for (String operator : manager.getAllOperators()) {
+            Operator operatorInstance = manager.operatorFor(operator);
+            precedenceMap.put(operator, operatorInstance.getPrecedence());
+            associativityMap.put(operator, operatorInstance.getAssociativity());
+            typeMap.put(operator, operatorInstance.getType());
+        }
+    }
+
+    @Override
+    public void onUnload(PluginManager manager) {
+        precedenceMap.clear();
+        associativityMap.clear();
+        typeMap.clear();
+    }
+}

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

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

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

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

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

@@ -0,0 +1,80 @@
+package org.nwapw.abacus.plugin;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+import java.util.stream.Collectors;
+
+/**
+ * Class that loads plugin classes from their jars.
+ */
+public class ClassFinder {
+
+    /**
+     * Loads all the plugin classes from the given plugin folder.
+     *
+     * @param filePath the path for the plugin folder.
+     * @return the list of all loaded classes.
+     * @throws IOException            thrown if an error occurred scanning the plugin folder.
+     * @throws ClassNotFoundException thrown if the class listed in the file doesn't get loaded.
+     */
+    public static List<Class<?>> loadJars(String filePath) throws IOException, ClassNotFoundException {
+        return loadJars(new File(filePath));
+    }
+
+    /**
+     * Loads all the plugin classes from the given plugin folder.
+     *
+     * @param pluginFolderPath the folder in which to look for plugins.
+     * @return the list of all loaded classes.
+     * @throws IOException            thrown if an error occurred scanning the plugin folder.
+     * @throws ClassNotFoundException thrown if the class listed in the file doesn't get loaded.
+     */
+    public static List<Class<?>> loadJars(File pluginFolderPath) throws IOException, ClassNotFoundException {
+        ArrayList<Class<?>> toReturn = new ArrayList<>();
+        if (!pluginFolderPath.exists()) return toReturn;
+        ArrayList<File> files = Files.walk(pluginFolderPath.toPath())
+                .map(Path::toFile)
+                .filter(f -> f.getName().endsWith(".jar"))
+                .collect(Collectors.toCollection(ArrayList::new));
+        for (File file : files) {
+            toReturn.addAll(loadJar(file));
+        }
+        return toReturn;
+    }
+
+    /**
+     * Loads the classes from a single path, given by the file.
+     *
+     * @param jarLocation the location of the jar to load.
+     * @return the list of loaded classes loaded from the jar.
+     * @throws IOException            thrown if there was an error reading the file
+     * @throws ClassNotFoundException thrown if the class could not be loaded.
+     */
+    public static List<Class<?>> loadJar(File jarLocation) throws IOException, ClassNotFoundException {
+        ArrayList<Class<?>> loadedClasses = new ArrayList<>();
+        String path = jarLocation.getPath();
+        URL[] urls = new URL[]{new URL("jar:file:" + path + "!/")};
+
+        URLClassLoader classLoader = URLClassLoader.newInstance(urls);
+        JarFile jarFolder = new JarFile(jarLocation);
+        Enumeration jarEntityList = jarFolder.entries();
+
+        while (jarEntityList.hasMoreElements()) {
+            JarEntry jarEntity = (JarEntry) jarEntityList.nextElement();
+            if (jarEntity.getName().endsWith(".class")) {
+                loadedClasses.add(classLoader.loadClass(jarEntity.getName().replace('/', '.').substring(0, jarEntity.getName().length() - 6)));
+            }
+        }
+        return loadedClasses;
+    }
+
+}

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

@@ -0,0 +1,81 @@
+package org.nwapw.abacus.plugin;
+
+import org.nwapw.abacus.number.NumberInterface;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+
+/**
+ * A class that holds data about a number implementation.
+ */
+public abstract class NumberImplementation {
+
+    /**
+     * The list of paths through which this implementation can be promoted.
+     */
+    private Map<Class<? extends NumberInterface>, Function<NumberInterface, NumberInterface>> promotionPaths;
+    /**
+     * The implementation class for this implementation.
+     */
+    private Class<? extends NumberInterface> implementation;
+    /**
+     * The priority of converting into this number implementation.
+     */
+    private int priority;
+
+    /**
+     * Creates a new number implementation with the given data.
+     *
+     * @param implementation the implementation class.
+     * @param priority       the priority, higher means more likely to be converted into.
+     */
+    public NumberImplementation(Class<? extends NumberInterface> implementation, int priority) {
+        this.implementation = implementation;
+        this.priority = priority;
+        promotionPaths = new HashMap<>();
+    }
+
+    /**
+     * 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() {
+        return promotionPaths;
+    }
+
+    /**
+     * Gets the implementation class used by this implementation.
+     *
+     * @return the implementation class.
+     */
+    public final Class<? extends NumberInterface> getImplementation() {
+        return implementation;
+    }
+
+    /**
+     * Gets the priority of this number implementation.
+     *
+     * @return the priority.
+     */
+    public final int getPriority() {
+        return priority;
+    }
+
+    /**
+     * Abstract function to create a new instance from a string.
+     *
+     * @param string the string to create a number from.
+     * @return the resulting number.
+     */
+    public abstract NumberInterface instanceForString(String string);
+
+    /**
+     * 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

@@ -0,0 +1,181 @@
+package org.nwapw.abacus.plugin;
+
+import org.nwapw.abacus.function.Documentation;
+import org.nwapw.abacus.function.DocumentationType;
+import org.nwapw.abacus.function.Function;
+import org.nwapw.abacus.function.Operator;
+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
+ * with the "hasFunction" and "getFunction" functions,
+ * and can use "registerFunction" and "functionFor" for
+ * loading internally.
+ */
+public abstract class Plugin {
+
+    /**
+     * The plugin manager in which to search for functions
+     * not inside this package,
+     */
+    private PluginManager manager;
+    /**
+     * Whether this plugin has been loaded.
+     */
+    private boolean enabled;
+
+    private Plugin() {
+    }
+
+    /**
+     * Creates a new plugin with the given PluginManager.
+     *
+     * @param manager the manager controlling this plugin.
+     */
+    public Plugin(PluginManager manager) {
+        this.manager = manager;
+        enabled = false;
+    }
+
+    /**
+     * Enables the function, loading the necessary instances
+     * of functions.
+     */
+    public final void enable() {
+        if (enabled) return;
+        onEnable();
+        enabled = true;
+    }
+
+    /**
+     * Disables the plugin, clearing loaded data store by default
+     * and calling its disable() method.
+     */
+    public final void disable() {
+        if (!enabled) return;
+        onDisable();
+        enabled = false;
+    }
+
+    /**
+     * To be used in load(). Registers a 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 function implementation.
+     */
+    protected final void registerFunction(String name, Function toRegister) {
+        manager.registerFunction(name, toRegister);
+    }
+
+    /**
+     * To be used in load(). Registers an operator abstract class
+     * with the plugin internally, which makes it accessible to
+     * the plugin manager.
+     *
+     * @param name     the name of the operator.
+     * @param operator the operator to register.
+     */
+    protected final void registerOperator(String name, Operator operator) {
+        manager.registerOperator(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) {
+        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);
+    }
+
+    /**
+     * 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 function, or null if none was found for that name.
+     */
+    protected final Function functionFor(String name) {
+        return manager.functionFor(name);
+    }
+
+    /**
+     * Searches the PluginManager for the given 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 operator, or null if none was found for that name.
+     */
+    protected final Operator operatorFor(String name) {
+        return manager.operatorFor(name);
+    }
+
+    /**
+     * Searches the PluginManager for the given number implementation
+     * name. This can be used by the plugins internally in order to find
+     * implementations that they do not provide.
+     *
+     * @param name the name for which to search.
+     * @return the resulting number implementation, or null if none was found.
+     */
+    protected final NumberImplementation numberImplementationFor(String name) {
+        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 piFor(Class<? extends NumberInterface> forClass) {
+        return manager.piFor(forClass);
+    }
+
+    /**
+     * Abstract method to be overridden by plugin implementation, in which the plugins
+     * are supposed to register the functions they provide and do any other
+     * necessary setup.
+     */
+    public abstract void onEnable();
+
+    /**
+     * Abstract method overridden by the plugin implementation, in which the plugins
+     * are supposed to dispose of loaded functions, operators, and macros.
+     */
+    public abstract void onDisable();
+
+}

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

@@ -0,0 +1,22 @@
+package org.nwapw.abacus.plugin;
+
+/**
+ * A listener that responds to changes in the PluginManager.
+ */
+public interface PluginListener {
+
+    /**
+     * Called when the PluginManager loads plugins.
+     *
+     * @param manager the manager that fired the event.
+     */
+    public void onLoad(PluginManager manager);
+
+    /**
+     * Called when the PluginManager unloads all its plugins.
+     *
+     * @param manager the manager that fired the event.
+     */
+    public void onUnload(PluginManager manager);
+
+}

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

@@ -0,0 +1,338 @@
+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.Function;
+import org.nwapw.abacus.function.Operator;
+import org.nwapw.abacus.number.NumberInterface;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.*;
+
+/**
+ * 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, Function> registeredFunctions;
+    /**
+     * The map of operators registered by the plugins
+     */
+    private Map<String, Operator> registeredOperators;
+    /**
+     * 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 implementations that have been
+     * found by their implementation class.
+     */
+    private Map<Class<? extends NumberInterface>, NumberImplementation> cachedInterfaceImplementations;
+    /**
+     * 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<>();
+        registeredOperators = new HashMap<>();
+        registeredNumberImplementations = new HashMap<>();
+        registeredDocumentation = new HashSet<>();
+        cachedInterfaceImplementations = 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, Function function){
+        registeredFunctions.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, Operator operator){
+        registeredOperators.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);
+    }
+
+    /**
+     * 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 Function functionFor(String name){
+        return registeredFunctions.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 Operator operatorFor(String name){
+        return registeredOperators.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;
+            }
+        }
+        if(toReturn == null){
+            toReturn = new Documentation(name, "", "", "", type);
+            registerDocumentation(toReturn);
+        }
+        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) {
+        if (cachedInterfaceImplementations.containsKey(name)) return cachedInterfaceImplementations.get(name);
+        NumberImplementation toReturn = null;
+        for(String key : registeredNumberImplementations.keySet()){
+            NumberImplementation implementation = registeredNumberImplementations.get(key);
+            if(implementation.getImplementation() == name) {
+                toReturn = implementation;
+                break;
+            }
+        }
+        cachedInterfaceImplementations.put(name, toReturn);
+        return toReturn;
+    }
+
+    /**
+     * 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) {
+        if (cachedPi.containsKey(forClass)) return cachedPi.get(forClass);
+        NumberImplementation implementation = interfaceImplementationFor(forClass);
+        NumberInterface generatedPi = null;
+        if (implementation != null) {
+            generatedPi = implementation.instanceForPi();
+        }
+        cachedPi.put(forClass, generatedPi);
+        return generatedPi;
+    }
+
+    /**
+     * 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();
+        registeredOperators.clear();
+        registeredNumberImplementations.clear();
+        registeredDocumentation.clear();
+        cachedInterfaceImplementations.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 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 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/StandardPlugin.java

@@ -0,0 +1,844 @@
+package org.nwapw.abacus.plugin;
+
+import org.nwapw.abacus.function.*;
+import org.nwapw.abacus.lexing.pattern.Match;
+import org.nwapw.abacus.number.NaiveNumber;
+import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.number.PreciseNumber;
+import org.nwapw.abacus.parsing.Parser;
+import org.nwapw.abacus.parsing.ShuntingYardParser;
+import org.nwapw.abacus.tree.TokenType;
+import org.nwapw.abacus.tree.TreeNode;
+
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.List;
+import java.util.function.BiFunction;
+
+/**
+ * The plugin providing standard functions such as addition and subtraction to
+ * the calculator.
+ */
+public class StandardPlugin extends Plugin {
+
+    /**
+     * Stores objects of NumberInterface with integer values for reuse.
+     */
+    private final static HashMap<Class<? extends NumberInterface>, HashMap<Integer, NumberInterface>> integerValues = new HashMap<>();
+
+    /**
+     * The addition operator, +
+     */
+    public static final Operator OP_ADD = new Operator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0, new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length >= 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            NumberInterface sum = params[0];
+            for (int i = 1; i < params.length; i++) {
+                sum = sum.add(params[i]);
+            }
+            return sum;
+        }
+    });
+    /**
+     * The subtraction operator, -
+     */
+    public static final Operator OP_SUBTRACT = new Operator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0, new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 2;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return params[0].subtract(params[1]);
+
+        }
+    });
+    /**
+     * The negation operator, -
+     */
+    public static final Operator OP_NEGATE = new Operator(OperatorAssociativity.LEFT, OperatorType.UNARY_PREFIX, 0, new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return params[0].negate();
+        }
+    });
+    /**
+     * The multiplication operator, *
+     */
+    public static final Operator OP_MULTIPLY = new Operator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1, new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length >= 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            NumberInterface product = params[0];
+            for (int i = 1; i < params.length; i++) {
+                product = product.multiply(params[i]);
+            }
+            return product;
+        }
+    });
+    /**
+     * The division operator, /
+     */
+    public static final Operator OP_DIVIDE = new Operator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1, new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 2 && params[1].compareTo(fromInt(params[0].getClass(), 0)) != 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return params[0].divide(params[1]);
+        }
+    });
+    /**
+     * The factorial operator, !
+     */
+    public static final Operator OP_FACTORIAL = new Operator(OperatorAssociativity.RIGHT, OperatorType.UNARY_POSTFIX, 0, new Function() {
+        //private HashMap<Class<? extends NumberInterface>, ArrayList<NumberInterface>> storedList = new HashMap<Class<? extends NumberInterface>, ArrayList<NumberInterface>>();
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1
+                    && params[0].fractionalPart().compareTo(fromInt(params[0].getClass(), 0)) == 0
+                    && params[0].signum() >= 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            if (params[0].signum() == 0) {
+                return fromInt(params[0].getClass(), 1);
+            }
+            NumberInterface one = fromInt(params[0].getClass(), 1);
+            NumberInterface factorial = params[0];
+            NumberInterface multiplier = params[0];
+            //It is necessary to later prevent calls of factorial on anything but non-negative integers.
+            while ((multiplier = multiplier.subtract(one)).signum() == 1) {
+                factorial = factorial.multiply(multiplier);
+            }
+            return factorial;
+                /*if(!storedList.containsKey(params[0].getClass())){
+                    storedList.put(params[0].getClass(), new ArrayList<NumberInterface>());
+                    storedList.get(params[0].getClass()).add(NaiveNumber.ONE.promoteTo(params[0].getClass()));
+                    storedList.get(params[0].getClass()).add(NaiveNumber.ONE.promoteTo(params[0].getClass()));
+                }*/
+        }
+    });
+    /**
+     * The permutation operator.
+     */
+    public static final Operator OP_NPR = new Operator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0, new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 2 && params[0].fractionalPart().signum() == 0
+                    && params[1].fractionalPart().signum() == 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            if(params[0].compareTo(params[1]) < 0 ||
+                    params[0].signum() < 0 ||
+                    (params[0].signum() == 0 && params[1].signum() != 0)) return fromInt(params[0].getClass(), 0);
+            NumberInterface total = fromInt(params[0].getClass(), 1);
+            NumberInterface multiplyBy = params[0];
+            NumberInterface remainingMultiplications = params[1];
+            NumberInterface halfway = params[0].divide(fromInt(params[0].getClass(), 2));
+            if(remainingMultiplications.compareTo(halfway) > 0){
+                remainingMultiplications = params[0].subtract(remainingMultiplications);
+            }
+            while(remainingMultiplications.signum() > 0){
+                total = total.multiply(multiplyBy);
+                remainingMultiplications = remainingMultiplications.subtract(fromInt(params[0].getClass(), 1));
+                multiplyBy = multiplyBy.subtract(fromInt(params[0].getClass(), 1));
+            }
+            return total;
+        }
+    });
+    /**
+     * The combination operator.
+     */
+    public static final Operator OP_NCR = new Operator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0, new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 2 && params[0].fractionalPart().signum() == 0
+                    && params[1].fractionalPart().signum() == 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return OP_NPR.getFunction().apply(params).divide(OP_FACTORIAL.getFunction().apply(params[1]));
+        }
+    });
+    /**
+     * The absolute value function, abs(-3) = 3
+     */
+    public static final Function FUNCTION_ABS = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return params[0].multiply(fromInt(params[0].getClass(), params[0].signum()));
+        }
+    };
+    /**
+     * The natural log function.
+     */
+    public static final Function FUNCTION_LN = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1 && params[0].compareTo(fromInt(params[0].getClass(), 0)) > 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            NumberInterface param = params[0];
+            NumberInterface one = fromInt(param.getClass(), 1);
+            int powersOf2 = 0;
+            while (FUNCTION_ABS.apply(param.subtract(one)).compareTo(new NaiveNumber(0.1).promoteTo(param.getClass())) >= 0) {
+                if (param.subtract(one).signum() == 1) {
+                    param = param.divide(fromInt(param.getClass(), 2));
+                    powersOf2++;
+                    if (param.subtract(one).signum() != 1) {
+                        break;
+                        //No infinite loop for you.
+                    }
+                } else {
+                    param = param.multiply(fromInt(param.getClass(), 2));
+                    powersOf2--;
+                    if (param.subtract(one).signum() != -1) {
+                        break;
+                        //No infinite loop for you.
+                    }
+                }
+            }
+            return getLog2(param).multiply(fromInt(param.getClass(), powersOf2)).add(getLogPartialSum(param));
+        }
+
+        /**
+         * Returns the partial sum of the Taylor series for logx (around x=1).
+         * Automatically determines the number of terms needed based on the precision of x.
+         * @param x value at which the series is evaluated. 0 < x < 2. (x=2 is convergent but impractical.)
+         * @return the partial sum.
+         */
+        private NumberInterface getLogPartialSum(NumberInterface x) {
+
+            NumberInterface maxError = x.getMaxError();
+            x = x.subtract(fromInt(x.getClass(), 1)); //Terms used are for log(x+1).
+            NumberInterface currentNumerator = x, currentTerm = x, sum = x;
+            int n = 1;
+            while (FUNCTION_ABS.apply(currentTerm).compareTo(maxError) > 0) {
+                n++;
+                currentNumerator = currentNumerator.multiply(x).negate();
+                currentTerm = currentNumerator.divide(fromInt(x.getClass(), n));
+                sum = sum.add(currentTerm);
+            }
+            return sum;
+        }
+
+        /**
+         * Returns natural log of 2 to the required precision of the class of number.
+         * @param number a number of the same type as the return type. (Used for precision.)
+         * @return the value of log(2) with the appropriate precision.
+         */
+        private NumberInterface getLog2(NumberInterface number) {
+            NumberInterface maxError = number.getMaxError();
+            //NumberInterface errorBound = fromInt(number.getClass(), 1);
+            //We'll use the series \sigma_{n >= 1) ((1/3^n + 1/4^n) * 1/n)
+            //In the following, a=1/3^n, b=1/4^n, c = 1/n.
+            //a is also an error bound.
+            NumberInterface a = fromInt(number.getClass(), 1), b = a, c = a;
+            NumberInterface sum = fromInt(number.getClass(), 0);
+            NumberInterface one = fromInt(number.getClass(), 1);
+            int n = 0;
+            while (a.compareTo(maxError) >= 1) {
+                n++;
+                a = a.divide(fromInt(number.getClass(), 3));
+                b = b.divide(fromInt(number.getClass(), 4));
+                c = one.divide(fromInt(number.getClass(), n));
+                sum = sum.add(a.add(b).multiply(c));
+            }
+            return sum;
+        }
+    };
+    /**
+     * The square root function.
+     */
+    public static final Function FUNCTION_SQRT = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return OP_CARET.getFunction().apply(params[0], ((new NaiveNumber(0.5)).promoteTo(params[0].getClass())));
+        }
+    };
+    /**
+     * Gets a random number smaller or equal to the given number's integer value.
+     */
+    public static final Function FUNCTION_RAND_INT = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return fromInt(params[0].getClass(), (int) Math.round(Math.random() * params[0].floor().intValue()));
+        }
+    };
+    /**
+     * 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() {
+            NumberInterface C = FUNCTION_SQRT.apply(new PreciseNumber("10005")).multiply(new PreciseNumber("426880"));
+            NumberInterface M = PreciseNumber.ONE;
+            NumberInterface L = new PreciseNumber("13591409");
+            NumberInterface X = M;
+            NumberInterface sum = L;
+            int termsNeeded = C.getMaxPrecision() / 13 + 1;
+
+            NumberInterface lSummand = new PreciseNumber("545140134");
+            NumberInterface xMultiplier = new PreciseNumber("262537412")
+                    .multiply(new PreciseNumber("1000000000"))
+                    .add(new PreciseNumber("640768000"))
+                    .negate();
+            for (int i = 0; i < termsNeeded; i++) {
+                M = M
+                        .multiply(new PreciseNumber((12 * i + 2) + ""))
+                        .multiply(new PreciseNumber((12 * i + 6) + ""))
+                        .multiply(new PreciseNumber((12 * i + 10) + ""))
+                        .divide(new PreciseNumber(Math.pow(i + 1, 3) + ""));
+                L = L.add(lSummand);
+                X = X.multiply(xMultiplier);
+                sum = sum.add(M.multiply(L).divide(X));
+            }
+            return C.divide(sum);
+        }
+    };
+    private static final HashMap<Class<? extends NumberInterface>, ArrayList<NumberInterface>> FACTORIAL_LISTS = new HashMap<>();
+    /**
+     * The exponential function, exp(1) = e^1 = 2.71...
+     */
+    public static final Function FUNCTION_EXP = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            NumberInterface maxError = params[0].getMaxError();
+            int n = 0;
+            if (params[0].signum() < 0) {
+                NumberInterface[] negatedParams = {params[0].negate()};
+               return fromInt(params[0].getClass(), 1).divide(applyInternal(negatedParams));
+            } else {
+                //We need n such that x^(n+1) * 3^ceil(x) <= maxError * (n+1)!.
+                //right and left refer to lhs and rhs in the above inequality.
+                NumberInterface sum = fromInt(params[0].getClass(), 1);
+                NumberInterface nextNumerator = params[0];
+                NumberInterface left = params[0].multiply(fromInt(params[0].getClass(), 3).intPow(params[0].ceiling().intValue())), right = maxError;
+                do {
+                    sum = sum.add(nextNumerator.divide(factorial(params[0].getClass(), n + 1)));
+                    n++;
+                    nextNumerator = nextNumerator.multiply(params[0]);
+                    left = left.multiply(params[0]);
+                    NumberInterface nextN = fromInt(params[0].getClass(), n + 1);
+                    right = right.multiply(nextN);
+                    //System.out.println(left + ", " + right);
+                }
+                while (left.compareTo(right) > 0);
+                //System.out.println(n+1);
+                return sum;
+            }
+        }
+    };
+    /**
+     * The caret / pow operator, ^
+     */
+    public static final Operator OP_CARET = new Operator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 2, new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            NumberInterface zero = fromInt(params[0].getClass(), 0);
+            return params.length == 2
+                    && !(params[0].compareTo(zero) == 0
+                    && params[1].compareTo(zero) == 0)
+                    && !(params[0].signum() == -1 && params[1].fractionalPart().compareTo(zero) != 0);
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            NumberInterface zero = fromInt(params[0].getClass(), 0);
+            if (params[0].compareTo(zero) == 0)
+                return zero;
+            else if (params[1].compareTo(zero) == 0)
+                return fromInt(params[0].getClass(), 1);
+            //Detect integer bases:
+            if(params[0].fractionalPart().compareTo(fromInt(params[0].getClass(), 0)) == 0
+                    && FUNCTION_ABS.apply(params[1]).compareTo(fromInt(params[0].getClass(), Integer.MAX_VALUE)) < 0
+                    && FUNCTION_ABS.apply(params[1]).compareTo(fromInt(params[1].getClass(), 1)) >= 0){
+                NumberInterface[] newParams = {params[0], params[1].fractionalPart()};
+                return params[0].intPow(params[1].floor().intValue()).multiply(applyInternal(newParams));
+            }
+            return FUNCTION_EXP.apply(FUNCTION_LN.apply(FUNCTION_ABS.apply(params[0])).multiply(params[1]));
+        }
+    });
+    /**
+     * The sine function (the argument is interpreted in radians).
+     */
+    public final Function functionSin = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            NumberInterface pi = piFor(params[0].getClass());
+            NumberInterface twoPi = pi.multiply(fromInt(pi.getClass(), 2));
+            NumberInterface theta = getSmallAngle(params[0], pi);
+            //System.out.println(theta);
+            if (theta.compareTo(pi.multiply(new NaiveNumber(1.5).promoteTo(twoPi.getClass()))) >= 0) {
+                theta = theta.subtract(twoPi);
+            } else if (theta.compareTo(pi.divide(fromInt(pi.getClass(), 2))) > 0) {
+                theta = pi.subtract(theta);
+            }
+            //System.out.println(theta);
+            return sinTaylor(theta);
+        }
+    };
+    /**
+     * The cosine function (the argument is in radians).
+     */
+    public final Function functionCos = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return functionSin.apply(piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
+                    .subtract(params[0]));
+        }
+    };
+    /**
+     * The tangent function (the argument is in radians).
+     */
+    public final Function functionTan = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return functionSin.apply(params[0]).divide(functionCos.apply(params[0]));
+        }
+    };
+    /**
+     * The secant function (the argument is in radians).
+     */
+    public final Function functionSec = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return fromInt(params[0].getClass(), 1).divide(functionCos.apply(params[0]));
+        }
+    };
+    /**
+     * The cosecant function (the argument is in radians).
+     */
+    public final Function functionCsc = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return fromInt(params[0].getClass(), 1).divide(functionSin.apply(params[0]));
+        }
+    };
+    /**
+     * The cotangent function (the argument is in radians).
+     */
+    public final Function functionCot = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return functionCos.apply(params[0]).divide(functionSin.apply(params[0]));
+        }
+    };
+
+    /**
+     * The arcsine function (return type in radians).
+     */
+    public final Function functionArcsin = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1
+                    && FUNCTION_ABS.apply(params[0]).compareTo(fromInt(params[0].getClass(), 1)) <= 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            if(FUNCTION_ABS.apply(params[0]).compareTo(new NaiveNumber(0.8).promoteTo(params[0].getClass())) >= 0){
+                NumberInterface[] newParams = {FUNCTION_SQRT.apply(fromInt(params[0].getClass(), 1).subtract(params[0].multiply(params[0])))};
+                return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
+                        .subtract(applyInternal(newParams)).multiply(fromInt(params[0].getClass(), params[0].signum()));
+            }
+            NumberInterface currentTerm = params[0], sum = currentTerm,
+                    multiplier = currentTerm.multiply(currentTerm), summandBound = sum.getMaxError().multiply(fromInt(sum.getClass(), 1).subtract(multiplier)),
+                    power = currentTerm, coefficient = fromInt(params[0].getClass(), 1);
+            int exponent = 1;
+            while(FUNCTION_ABS.apply(currentTerm).compareTo(summandBound) > 0){
+                exponent += 2;
+                power = power.multiply(multiplier);
+                coefficient = coefficient.multiply(fromInt(params[0].getClass(), exponent-2))
+                        .divide(fromInt(params[0].getClass(), exponent - 1));
+                currentTerm = power.multiply(coefficient).divide(fromInt(power.getClass(), exponent));
+                sum = sum.add(currentTerm);
+            }
+            return sum;
+        }
+    };
+
+    /**
+     * The arccosine function.
+     */
+    public final Function functionArccos = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(params[0]).compareTo(fromInt(params[0].getClass(), 1)) <= 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
+                    .subtract(functionArcsin.apply(params));
+        }
+    };
+
+    /**
+     * The arccosecant function.
+     */
+    public final Function functionArccsc = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(params[0]).compareTo(fromInt(params[0].getClass(), 1)) >= 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            NumberInterface[] reciprocalParamArr = {fromInt(params[0].getClass(), 1).divide(params[0])};
+            return functionArcsin.apply(reciprocalParamArr);
+        }
+    };
+
+    /**
+     * The arcsecant function.
+     */
+    public final Function functionArcsec = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1 && FUNCTION_ABS.apply(params[0]).compareTo(fromInt(params[0].getClass(), 1)) >= 0;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            NumberInterface[] reciprocalParamArr = {fromInt(params[0].getClass(), 1).divide(params[0])};
+            return functionArccos.apply(reciprocalParamArr);
+        }
+    };
+
+    /**
+     * The arctangent function.
+     */
+    public final Function functionArctan = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            if(params[0].signum() == -1){
+                NumberInterface[] negatedParams = {params[0].negate()};
+                return applyInternal(negatedParams).negate();
+            }
+            if(params[0].compareTo(fromInt(params[0].getClass(), 1)) > 0){
+                NumberInterface[] reciprocalParams = {fromInt(params[0].getClass(), 1).divide(params[0])};
+                return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
+                        .subtract(applyInternal(reciprocalParams));
+            }
+            if(params[0].compareTo(fromInt(params[0].getClass(), 1)) == 0){
+                return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 4));
+            }
+            if(params[0].compareTo(new NaiveNumber(0.9).promoteTo(params[0].getClass())) >= 0){
+                NumberInterface[] newParams = {params[0].multiply(fromInt(params[0].getClass(),2 ))
+                .divide(fromInt(params[0].getClass(), 1).subtract(params[0].multiply(params[0])))};
+                return applyInternal(newParams).divide(fromInt(params[0].getClass(), 2));
+            }
+            NumberInterface currentPower = params[0], currentTerm = currentPower, sum = currentTerm,
+                    maxError = params[0].getMaxError(), multiplier = currentPower.multiply(currentPower).negate();
+            int n = 1;
+            while(FUNCTION_ABS.apply(currentTerm).compareTo(maxError) > 0){
+                n += 2;
+                currentPower = currentPower.multiply(multiplier);
+                currentTerm = currentPower.divide(fromInt(currentPower.getClass(), n));
+                sum = sum.add(currentTerm);
+            }
+            return sum;
+        }
+    };
+
+    /**
+     * The arccotangent function. Range: (0, pi).
+     */
+    public final Function functionArccot = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 1;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(NumberInterface[] params) {
+            return piFor(params[0].getClass()).divide(fromInt(params[0].getClass(), 2))
+                    .subtract(functionArctan.apply(params));
+        }
+    };
+
+    public StandardPlugin(PluginManager manager) {
+        super(manager);
+    }
+
+    /**
+     * Returns a partial sum of a series whose terms are given by the nthTermFunction, evaluated at x.
+     *
+     * @param x               the value at which the series is evaluated.
+     * @param nthTermFunction the function that returns the nth term of the series, in the format term(x, n).
+     * @param n               the number of terms in the partial sum.
+     * @return the value of the partial sum that has the same class as x.
+     */
+    private static NumberInterface sumSeries(NumberInterface x, BiFunction<Integer, NumberInterface, NumberInterface> nthTermFunction, int n) {
+        NumberInterface sum = fromInt(x.getClass(), 0);
+        for (int i = 0; i <= n; i++) {
+            sum = sum.add(nthTermFunction.apply(i, x));
+        }
+        return sum;
+    }
+
+    /**
+     * A factorial function that uses memoization for each number class; it efficiently
+     * computes factorials of non-negative integers.
+     *
+     * @param numberClass type of number to return.
+     * @param n           non-negative integer.
+     * @return a number of numClass with value n factorial.
+     */
+    public static NumberInterface factorial(Class<? extends NumberInterface> numberClass, int n) {
+        if (!FACTORIAL_LISTS.containsKey(numberClass)) {
+            FACTORIAL_LISTS.put(numberClass, new ArrayList<>());
+            FACTORIAL_LISTS.get(numberClass).add(fromInt(numberClass, 1));
+            FACTORIAL_LISTS.get(numberClass).add(fromInt(numberClass, 1));
+        }
+        ArrayList<NumberInterface> list = FACTORIAL_LISTS.get(numberClass);
+        if (n >= list.size()) {
+            while (list.size() < n + 16) {
+                list.add(list.get(list.size() - 1).multiply(fromInt(numberClass, list.size())));
+            }
+        }
+        return list.get(n);
+    }
+
+    /**
+     * Returns the value of the Taylor series for sin (centered at 0) at x.
+     *
+     * @param x where the series is evaluated.
+     * @return the value of the series
+     */
+    private static NumberInterface sinTaylor(NumberInterface x) {
+        NumberInterface power = x, multiplier = x.multiply(x).negate(), currentTerm = x, sum = x;
+        NumberInterface maxError = x.getMaxError();
+        int n = 1;
+        do {
+            n += 2;
+            power = power.multiply(multiplier);
+            currentTerm = power.divide(factorial(x.getClass(), n));
+            sum = sum.add(currentTerm);
+        } while (FUNCTION_ABS.apply(currentTerm).compareTo(maxError) > 0);
+        return sum;
+    }
+
+    /**
+     * Returns an equivalent angle in the interval [0, 2pi)
+     *
+     * @param phi an angle (in radians).
+     * @return theta in [0, 2pi) that differs from phi by a multiple of 2pi.
+     */
+    private static NumberInterface getSmallAngle(NumberInterface phi, NumberInterface pi) {
+        NumberInterface twoPi = pi.multiply(fromInt(pi.getClass(), 2));
+        NumberInterface theta = FUNCTION_ABS.apply(phi).subtract(twoPi
+                .multiply(FUNCTION_ABS.apply(phi).divide(twoPi).floor())); //Now theta is in [0, 2pi).
+        if (phi.signum() < 0) {
+            theta = twoPi.subtract(theta);
+        }
+        return theta;
+    }
+
+    /**
+     * Returns a number of class numType with value n.
+     * @param numType class of number to return.
+     * @param n value of returned number.
+     * @return numClass instance with value n.
+     */
+    private static NumberInterface fromInt(Class<? extends NumberInterface> numType, int n){
+        if(!integerValues.containsKey(numType)){
+            integerValues.put(numType, new HashMap<>());
+        }
+        if(!integerValues.get(numType).containsKey(n)){
+            integerValues.get(numType).put(n, new NaiveNumber(n).promoteTo(numType));
+        }
+        return integerValues.get(numType).get(n);
+    }
+
+    @Override
+    public void onEnable() {
+        registerNumberImplementation("naive", IMPLEMENTATION_NAIVE);
+        registerNumberImplementation("precise", IMPLEMENTATION_PRECISE);
+
+        registerOperator("+", OP_ADD);
+        registerOperator("-", OP_SUBTRACT);
+        registerOperator("`", OP_NEGATE);
+        registerOperator("*", OP_MULTIPLY);
+        registerOperator("/", OP_DIVIDE);
+        registerOperator("^", OP_CARET);
+        registerOperator("!", OP_FACTORIAL);
+
+        registerOperator("nPr", OP_NPR);
+        registerOperator("nCr", OP_NCR);
+
+        registerFunction("abs", FUNCTION_ABS);
+        registerFunction("exp", FUNCTION_EXP);
+        registerFunction("ln", FUNCTION_LN);
+        registerFunction("sqrt", FUNCTION_SQRT);
+
+        registerFunction("sin", functionSin);
+        registerFunction("cos", functionCos);
+        registerFunction("tan", functionTan);
+        registerFunction("sec", functionSec);
+        registerFunction("csc", functionCsc);
+        registerFunction("cot", functionCot);
+
+        registerFunction("arcsin", functionArcsin);
+        registerFunction("arccos", functionArccos);
+        registerFunction("arctan", functionArctan);
+        registerFunction("arcsec", functionArcsec);
+        registerFunction("arccsc", functionArccsc);
+        registerFunction("arccot", functionArccot);
+
+        registerFunction("random_int", FUNCTION_RAND_INT);
+
+        registerDocumentation(new Documentation("abs", "Absolute Value", "Finds the distance " +
+                "from zero of a number.", "Given a number, this function finds the distance form " +
+                "zero of a number, effectively turning negative numbers into positive ones.\n\n" +
+                "Example: abs(-2) -> 2", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("exp", "Exponentiate", "Brings e to the given power.",
+                "This function evaluates e to the power of the given value, and is the inverse " +
+                        "of the natural logarithm.\n\n" +
+                        "Example: exp(1) -> 2.718...", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("ln", "Natural Logarithm", "Gets the natural " +
+                "logarithm of the given value.", "The natural logarithm of a number is " +
+                "the power that e has to be brought to to be equal to the number.\n\n" +
+                "Example: ln(2.718) -> 1", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("sqrt", "Square Root", "Finds the square root " +
+                "of the number.", "A square root a of a number is defined as the non-negative a such that a times a is equal " +
+                "to that number.\n\n" +
+                "Example: sqrt(4) -> 2", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("sin", "Sine", "Computes the sine of the given angle, " +
+                "in radians.", "Example: sin(pi/6) -> 0.5", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("cos", "Cosine", "Computes the cosine of the given angle, " +
+                "in radians.", "Example: cos(pi/6) -> 0.866... (the exact result is sqrt(3)/2)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("tan", "Tangent", "Computes the tangent of the given angle, " +
+                "in radians.", "Example: tan(pi/6) -> 0.577... (the exact result is 1/sqrt(3))", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("sec", "Secant", "Computes the secant of the given angle, " +
+                "in radians.", "Example: sec(pi/6) -> 1.154... (the exact result is 2/sqrt(3))", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("csc", "Cosecant", "Computes the cosecant of the given angle, " +
+                "in radians.", "Example: csc(pi/6) -> 2", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("cot", "Cotangent", "Computes the cotangent of the given angle, " +
+                "in radians.", "Example: cot(pi/6) -> 1.732... (the exact result is sqrt(3))", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("random_int", "Random Integer", "Generates a random integer [0, n].",
+                "Generates a pseudorandom number using the standard JVM random mechanism, keeping it less than or " +
+                        "equal to the given number.\n\n" +
+                        "Example: random_int(5) -> 4\n" +
+                        "random_int(5) -> 3\n" +
+                        "random_int(5) -> 3\n", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arcsin", "Arcsine", "Computes the arcsine of x. (The result is in radians.)",
+                "Example: arcsin(0.5) -> 0.523... (the exact result is pi/6)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arccos", "Arccosine", "Computes the arccosine of x. (The result is in radians.)",
+                "Example: arccos(0.5) -> 1.047... (the exact result is pi/3)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arctan", "Arctangent", "Computes the arctangent of x. (The result is in radians.)",
+                "Example: arctan(1) -> 0.785... (the exact result is pi/4)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arcsec", "Arcsecant", "Computes the arcsecant of x. (The result is in radians.)",
+                "Example: arcsec(2) -> 1.047... (the exact result is pi/3)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arccsc", "Arccosecant", "Computes the arcscosecant of x. (The result is in radians.)",
+                "Example: arccsc(2) -> 0.523... (the exact result is pi/6)", DocumentationType.FUNCTION));
+        registerDocumentation(new Documentation("arccot", "Arccotangent", "Computes the arccotangent of x. (The result is in radians," +
+                " in the range (0, pi).)",
+                "Example: arccot(0) -> 1.570... (the exact result is pi/2)", DocumentationType.FUNCTION));
+    }
+
+    @Override
+    public void onDisable() {
+
+    }
+}

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

@@ -0,0 +1,54 @@
+package org.nwapw.abacus.tree;
+
+import org.nwapw.abacus.Abacus;
+import org.nwapw.abacus.function.Function;
+import org.nwapw.abacus.number.NumberInterface;
+
+/**
+ * A reducer implementation that turns a tree into a single number.
+ * This is not always guaranteed to work.
+ */
+public class NumberReducer implements Reducer<NumberInterface> {
+
+    /**
+     * The plugin manager from which to draw the functions.
+     */
+    private Abacus abacus;
+
+    /**
+     * Creates a new number reducer.
+     *
+     * @param abacus the calculator instance.
+     */
+    public NumberReducer(Abacus abacus) {
+        this.abacus = abacus;
+    }
+
+    @Override
+    public NumberInterface reduceNode(TreeNode node, Object... children) {
+        if (node instanceof NumberNode) {
+            return ((NumberNode) node).getNumber();
+        } else if (node instanceof BinaryNode) {
+            NumberInterface left = (NumberInterface) children[0];
+            NumberInterface right = (NumberInterface) children[1];
+            Function function = abacus.getPluginManager().operatorFor(((BinaryNode) node).getOperation()).getFunction();
+            if (function == null) return null;
+            return function.apply(left, right);
+        } else if (node instanceof UnaryNode) {
+            NumberInterface child = (NumberInterface) children[0];
+            Function functionn = abacus.getPluginManager().operatorFor(((UnaryNode) node).getOperation()).getFunction();
+            if (functionn == null) return null;
+            return functionn.apply(child);
+        } else if (node instanceof FunctionNode) {
+            NumberInterface[] convertedChildren = new NumberInterface[children.length];
+            for (int i = 0; i < convertedChildren.length; i++) {
+                convertedChildren[i] = (NumberInterface) children[i];
+            }
+            Function function = abacus.getPluginManager().functionFor(((FunctionNode) node).getFunction());
+            if (function == null) return null;
+            return function.apply(convertedChildren);
+        }
+        return null;
+    }
+
+}

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

@@ -0,0 +1,26 @@
+package org.nwapw.abacus.tree;
+
+/**
+ * Enum to represent the type of the token that has been matched
+ * by the lexer.
+ */
+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);
+
+    /**
+     * The priority by which this token gets sorted.
+     */
+    public final int priority;
+
+    /**
+     * Creates a new token type with the given priority.
+     *
+     * @param priority the priority of this token type.
+     */
+    TokenType(int priority) {
+        this.priority = priority;
+    }
+
+}

core/src/main/java/org/nwapw/abacus/window/HistoryTableModel.java

@@ -0,0 +1,106 @@
+package org.nwapw.abacus.window;
+
+import org.nwapw.abacus.tree.TreeNode;
+
+import javax.swing.table.AbstractTableModel;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A table model to store data about the history of inputs
+ * in the calculator.
+ */
+public class HistoryTableModel extends AbstractTableModel {
+
+    /**
+     * Static array used to get the column names.
+     */
+    public static final String[] COLUMN_NAMES = {
+            "Input",
+            "Parsed Input",
+            "Output"
+    };
+
+    /**
+     * Static array used to get the class of each column.
+     */
+    public static final Class[] CLASS_TYPES = {
+            String.class,
+            TreeNode.class,
+            String.class
+    };
+    /**
+     * The list of entries.
+     */
+    List<HistoryEntry> entries;
+
+    /**
+     * Creates a new empty history table model
+     */
+    public HistoryTableModel() {
+        entries = new ArrayList<>();
+    }
+
+    /**
+     * Adds an entry to the model.
+     *
+     * @param entry the entry to add.
+     */
+    public void addEntry(HistoryEntry entry) {
+        entries.add(entry);
+    }
+
+    @Override
+    public int getRowCount() {
+        return entries.size();
+    }
+
+    @Override
+    public int getColumnCount() {
+        return 3;
+    }
+
+    @Override
+    public String getColumnName(int columnIndex) {
+        return COLUMN_NAMES[columnIndex];
+    }
+
+    @Override
+    public Class<?> getColumnClass(int columnIndex) {
+        return CLASS_TYPES[columnIndex];
+    }
+
+    @Override
+    public boolean isCellEditable(int rowIndex, int columnIndex) {
+        return false;
+    }
+
+    @Override
+    public Object getValueAt(int rowIndex, int columnIndex) {
+        return entries.get(rowIndex).nthValue(columnIndex);
+    }
+
+    /**
+     * Class used specifically to hold data about
+     * the previous entries into the calculator.
+     */
+    public static class HistoryEntry {
+        public String input;
+        public TreeNode parsedInput;
+        public String output;
+
+        public HistoryEntry(String input, TreeNode parsedInput, String output) {
+            this.input = input;
+            this.parsedInput = parsedInput;
+            this.output = output;
+        }
+
+        Object nthValue(int n) {
+            if (n == 0) return input;
+            if (n == 1) return parsedInput;
+            if (n == 2) return output;
+            return null;
+        }
+    }
+
+}

core/src/main/java/org/nwapw/abacus/window/Window.java

@@ -0,0 +1,255 @@
+package org.nwapw.abacus.window;
+
+import org.nwapw.abacus.Abacus;
+import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.tree.TreeNode;
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.datatransfer.StringSelection;
+import java.awt.event.ActionListener;
+import java.awt.event.MouseAdapter;
+import java.awt.event.MouseEvent;
+
+/**
+ * The main UI window for the calculator.
+ */
+public class Window extends JFrame {
+
+    private static final String CALC_STRING = "Calculate";
+    private static final String SYNTAX_ERR_STRING = "Syntax Error";
+    private static final String EVAL_ERR_STRING = "Evaluation Error";
+    private static final String NUMBER_SYSTEM_LABEL = "Number Type:";
+    private static final String FUNCTION_LABEL = "Functions:";
+
+    /**
+     * Array of Strings to which the "calculate" button's text
+     * changes. For instance, in the graph tab, the name will
+     * be "Graph" and not "Calculate".
+     */
+    private static final String[] BUTTON_NAMES = {
+            CALC_STRING,
+            CALC_STRING
+    };
+
+    /**
+     * Array of booleans that determine whether the input
+     * field and the input button are enabled at a particular
+     * index.
+     */
+    private static boolean[] INPUT_ENABLED = {
+            true,
+            false
+    };
+
+    /**
+     * The instance of the Abacus class, used
+     * for interaction with plugins and configuration.
+     */
+    private Abacus abacus;
+    /**
+     * The last output by the calculator.
+     */
+    private String lastOutput;
+
+    /**
+     * The tabbed pane that separates calculator contexts.
+     */
+    private JTabbedPane pane;
+
+    /**
+     * The panel where the output occurs.
+     */
+    private JPanel calculationPanel;
+    /**
+     * The text area reserved for the last output.
+     */
+    private JTextArea lastOutputArea;
+    /**
+     * The table used for storing history results.
+     */
+    private JTable historyTable;
+    /**
+     * The table model used for managing history.
+     */
+    private HistoryTableModel historyModel;
+    /**
+     * The scroll pane for the history area.
+     */
+    private JScrollPane historyScroll;
+
+    /**
+     * The panel where the input occurs.
+     */
+    private JPanel inputPanel;
+    /**
+     * The input text field.
+     */
+    private JTextField inputField;
+    /**
+     * The "submit" button.
+     */
+    private JButton inputEnterButton;
+
+    /**
+     * The side panel for separate configuration.
+     */
+    private JPanel settingsPanel;
+    /**
+     * Panel for elements relating to number
+     * system selection.
+     */
+    private JPanel numberSystemPanel;
+    /**
+     * The possible list of number systems.
+     */
+    private JComboBox<String> numberSystemList;
+    /**
+     * The panel for elements relating to
+     * function selection.
+     */
+    private JPanel functionSelectPanel;
+    /**
+     * The list of functions available to the user.
+     */
+    private JComboBox<String> functionList;
+
+    /**
+     * Action listener that causes the input to be evaluated.
+     */
+    private ActionListener evaluateListener = (event) -> {
+        TreeNode parsedExpression = abacus.parseString(inputField.getText());
+        if (parsedExpression == null) {
+            lastOutputArea.setText(SYNTAX_ERR_STRING);
+            return;
+        }
+        NumberInterface numberInterface = abacus.evaluateTree(parsedExpression);
+        if (numberInterface == null) {
+            lastOutputArea.setText(EVAL_ERR_STRING);
+            return;
+        }
+        lastOutput = numberInterface.toString();
+        historyModel.addEntry(new HistoryTableModel.HistoryEntry(inputField.getText(), parsedExpression, lastOutput));
+        historyTable.invalidate();
+        lastOutputArea.setText(lastOutput);
+        inputField.setText("");
+    };
+
+    /**
+     * Array of listeners that tell the input button how to behave
+     * at a given input tab.
+     */
+    private ActionListener[] listeners = {
+            evaluateListener,
+            null
+    };
+
+    /**
+     * Creates a new window with the given manager.
+     *
+     * @param abacus the calculator instance to interact with other components.
+     */
+    public Window(Abacus abacus) {
+        this();
+        this.abacus = abacus;
+    }
+
+    /**
+     * Creates a new window.
+     */
+    private Window() {
+        super();
+
+        lastOutput = "";
+
+        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
+        setSize(320, 480);
+
+        inputField = new JTextField();
+        inputEnterButton = new JButton(CALC_STRING);
+
+        inputPanel = new JPanel();
+        inputPanel.setLayout(new BorderLayout());
+        inputPanel.add(inputField, BorderLayout.CENTER);
+        inputPanel.add(inputEnterButton, BorderLayout.SOUTH);
+
+        historyModel = new HistoryTableModel();
+        historyTable = new JTable(historyModel);
+        historyScroll = new JScrollPane(historyTable);
+        lastOutputArea = new JTextArea(lastOutput);
+        lastOutputArea.setEditable(false);
+
+        calculationPanel = new JPanel();
+        calculationPanel.setLayout(new BorderLayout());
+        calculationPanel.add(historyScroll, BorderLayout.CENTER);
+        calculationPanel.add(lastOutputArea, BorderLayout.SOUTH);
+
+        numberSystemList = new JComboBox<>();
+
+        numberSystemPanel = new JPanel();
+        numberSystemPanel.setAlignmentX(Component.LEFT_ALIGNMENT);
+        numberSystemPanel.setLayout(new FlowLayout());
+        numberSystemPanel.add(new JLabel(NUMBER_SYSTEM_LABEL));
+        numberSystemPanel.add(numberSystemList);
+        numberSystemPanel.setMaximumSize(numberSystemPanel.getPreferredSize());
+
+        functionList = new JComboBox<>();
+
+        functionSelectPanel = new JPanel();
+        functionSelectPanel.setAlignmentX(Component.LEFT_ALIGNMENT);
+        functionSelectPanel.setLayout(new FlowLayout());
+        functionSelectPanel.add(new JLabel(FUNCTION_LABEL));
+        functionSelectPanel.add(functionList);
+        functionSelectPanel.setMaximumSize(functionSelectPanel.getPreferredSize());
+
+        settingsPanel = new JPanel();
+        settingsPanel.setAlignmentX(Component.LEFT_ALIGNMENT);
+        settingsPanel.setLayout(new BoxLayout(settingsPanel, BoxLayout.PAGE_AXIS));
+        settingsPanel.add(numberSystemPanel);
+        settingsPanel.add(functionSelectPanel);
+
+        pane = new JTabbedPane();
+        pane.add("Calculator", calculationPanel);
+        pane.add("Settings", settingsPanel);
+        pane.addChangeListener(e -> {
+            int selectionIndex = pane.getSelectedIndex();
+            boolean enabled = INPUT_ENABLED[selectionIndex];
+            ActionListener listener = listeners[selectionIndex];
+            inputEnterButton.setText(BUTTON_NAMES[selectionIndex]);
+            inputField.setEnabled(enabled);
+            inputEnterButton.setEnabled(enabled);
+
+            for (ActionListener removingListener : inputEnterButton.getActionListeners()) {
+                inputEnterButton.removeActionListener(removingListener);
+                inputField.removeActionListener(removingListener);
+            }
+            if (listener != null) {
+                inputEnterButton.addActionListener(listener);
+                inputField.addActionListener(listener);
+            }
+        });
+        add(pane, BorderLayout.CENTER);
+        add(inputPanel, BorderLayout.SOUTH);
+
+        inputEnterButton.addActionListener(evaluateListener);
+        inputField.addActionListener(evaluateListener);
+        historyTable.addMouseListener(new MouseAdapter() {
+            @Override
+            public void mouseClicked(MouseEvent e) {
+                Point clickPoint = e.getPoint();
+                if (e.getClickCount() == 2) {
+                    int row = historyTable.rowAtPoint(clickPoint);
+                    int column = historyTable.columnAtPoint(clickPoint);
+                    String toCopy = historyTable.getValueAt(row, column).toString();
+                    Toolkit.getDefaultToolkit().getSystemClipboard().setContents(new StringSelection(toCopy), null);
+                }
+            }
+        });
+    }
+
+    @Override
+    public void setVisible(boolean b) {
+        super.setVisible(b);
+        if (b) inputField.requestFocusInWindow();
+    }
+}

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 +1,14 @@
+package org.nwapw.abacus.function
+
+/**
+ * A single operator that can be used by Abacus.
+ *
+ * This is a data 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.
+ * @param function the function this operator applies to its arguments.
+ */
+data class Operator(val associativity: OperatorAssociativity, val type: OperatorType,
+                    val precedence: Int, val function: Function)

core/src/main/kotlin/org/nwapw/abacus/fx/HistoryModel.kt

@@ -0,0 +1,32 @@
+package org.nwapw.abacus.fx
+
+import javafx.beans.property.SimpleStringProperty
+
+/**
+ * A model representing an input / output in the calculator.
+ *
+ * The HistoryModel class stores a record of a single user-provided input,
+ * its parsed form as it was interpreted by the calculator, and the output
+ * that was provided by the calculator. These are represented as properties
+ * to allow easy access by JavaFX cells.
+ *
+ * @param input the user input
+ * @param parsed the parsed version of the input.
+ * @param output the output string.
+ */
+class HistoryModel(input: String, parsed: String, output: String){
+
+    /**
+     * The property that holds the input.
+     */
+    val inputProperty = SimpleStringProperty(input)
+    /**
+     * The property that holds the parsed input.
+     */
+    val parsedProperty = SimpleStringProperty(parsed)
+    /**
+     * The property that holds the output.
+     */
+    val outputProperty = SimpleStringProperty(output)
+
+}

core/src/main/kotlin/org/nwapw/abacus/fx/ToggleablePlugin.kt

@@ -0,0 +1,31 @@
+package org.nwapw.abacus.fx
+
+import javafx.beans.property.SimpleBooleanProperty
+
+/**
+ * A model representing a plugin that can be disabled or enabled.
+ *
+ * ToggleablePlugin is a model that is used to present to the user the option
+ * of disabling / enabling plugins. The class name in this plugin is stored if
+ * its "enabledPropery" is false, essentially blacklisting the plugin.
+ *
+ * @param className the name of the class that this model concerns.
+ * @param enabled whether or not the model should start enabled.
+ */
+class ToggleablePlugin (val className: String, enabled: Boolean) {
+
+    /**
+     * The property used to interact with JavaFX components.
+     */
+    val enabledProperty = SimpleBooleanProperty(enabled)
+
+    /**
+     * Checks whether this plugin is currently enabled or not.
+     *
+     * @return true if it is enabled, false otherwise.
+     */
+    fun isEnabled(): Boolean {
+        return enabledProperty.value
+    }
+
+}

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

@@ -0,0 +1,26 @@
+package org.nwapw.abacus.tree
+
+/**
+ * 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.
+ */
+data class BinaryNode(val operation: String, val left: TreeNode? = null, val right: TreeNode?) : TreeNode() {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+        val leftReduce = left?.reduce(reducer) ?: return null
+        val rightReduce = right?.reduce(reducer) ?: return null
+        return reducer.reduceNode(this, leftReduce, rightReduce)
+    }
+
+    override fun toString(): String {
+        return "(" + (left?.toString() ?: "null") + operation + (right?.toString() ?: "null") + ")"
+    }
+
+}

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

@@ -0,0 +1,52 @@
+package org.nwapw.abacus.tree
+
+/**
+ * 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.
+ */
+data class FunctionNode(val function: String) : TreeNode() {
+
+    /**
+     * List of function parameters added to this node.
+     */
+    val children: MutableList<TreeNode> = mutableListOf()
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+        val children = Array<Any>(children.size, { children[it].reduce(reducer) ?: return null; })
+        return reducer.reduceNode(this, *children)
+    }
+
+    override fun toString(): String {
+        val buffer = StringBuffer()
+        buffer.append(function)
+        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()
+    }
+
+    /**
+     * Appends a child to this node's list of children.
+     *
+     * @node the node to append.
+     */
+    fun appendChild(node: TreeNode){
+        children.add(node)
+    }
+
+    /**
+     * Prepends a child to this node's list of children.
+     *
+     * @node the node to prepend.
+     */
+    fun prependChild(node: TreeNode){
+        children.add(0, node)
+    }
+
+}

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

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.tree
+
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * 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.
+ */
+data class NumberNode(val number: NumberInterface) : TreeNode() {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+        return reducer.reduceNode(this)
+    }
+
+    override fun toString(): String {
+        return number.toString()
+    }
+
+}

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

@@ -0,0 +1,19 @@
+package org.nwapw.abacus.tree
+
+/**
+ * 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/TreeNode.kt

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

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

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.tree
+
+/**
+ * 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.
+ */
+data class UnaryNode(val operation: String, val applyTo: TreeNode? = null) : TreeNode() {
+
+    override fun <T : Any> reduce(reducer: Reducer<T>): T? {
+        val reducedChild = applyTo?.reduce(reducer) ?: return null
+        return reducer.reduceNode(this, reducedChild)
+    }
+
+    override fun toString(): String {
+        return "(" + (applyTo?.toString() ?: "null") + ")" + operation
+    }
+
+}

core/src/main/resources/abacus.fxml

@@ -0,0 +1,76 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<?import javafx.geometry.Insets?>
+<?import javafx.scene.control.*?>
+<?import javafx.scene.layout.*?>
+<?import javafx.scene.text.Text?>
+<BorderPane xmlns:fx="http://javafx.com/fxml"
+            xmlns="http://javafx.com/javafx"
+            fx:controller="org.nwapw.abacus.fx.AbacusController">
+    <center>
+        <TabPane fx:id="coreTabPane">
+            <Tab fx:id="calculateTab" text="Calculator" closable="false">
+                <BorderPane>
+                    <center>
+                        <TableView fx:id="historyTable">
+                            <columnResizePolicy>
+                                <TableView fx:constant="CONSTRAINED_RESIZE_POLICY"/>
+                            </columnResizePolicy>
+                            <columns>
+                                <TableColumn fx:id="inputColumn" text="Input" sortable="false"/>
+                                <TableColumn fx:id="parsedColumn" text="Parsed" sortable="false"/>
+                                <TableColumn fx:id="outputColumn" text="Output" sortable="false"/>
+                            </columns>
+                        </TableView>
+                    </center>
+                    <bottom>
+                        <VBox>
+                            <ScrollPane prefHeight="50" vbarPolicy="NEVER">
+                                <padding>
+                                    <Insets top="10" bottom="10" left="10" right="10"/>
+                                </padding>
+                                <Text fx:id="outputText"/>
+                            </ScrollPane>
+                            <TextField fx:id="inputField" onAction="#performCalculation"/>
+                            <Button fx:id="inputButton" text="Calculate" maxWidth="Infinity"
+                                    onAction="#performCalculation"/>
+                            <Button fx:id="stopButton" text="Stop" maxWidth="Infinity"
+                                    onAction="#performStop" disable="true"/>
+                        </VBox>
+                    </bottom>
+                </BorderPane>
+            </Tab>
+            <Tab fx:id="settingsTab" text="Settings" closable="false">
+                <GridPane hgap="10" vgap="10">
+                    <padding>
+                        <Insets left="10" right="10" top="10" bottom="10"/>
+                    </padding>
+                    <Label text="Number Implementation" GridPane.columnIndex="0" GridPane.rowIndex="0"/>
+                    <ComboBox fx:id="numberImplementationBox" GridPane.columnIndex="1" GridPane.rowIndex="0"/>
+                    <ListView fx:id="enabledPluginView"
+                              GridPane.rowIndex="1" GridPane.columnIndex="0"
+                              GridPane.columnSpan="2" maxHeight="100"/>
+                    <Text GridPane.columnIndex="0" GridPane.rowIndex="2" text="Computation Limit"/>
+                    <TextField fx:id="computationLimitField" GridPane.columnIndex="1" GridPane.rowIndex="2"/>
+                    <FlowPane GridPane.columnIndex="0" GridPane.columnSpan="2" GridPane.rowIndex="3" hgap="10"
+                              vgap="10">
+                        <Button text="Apply" onAction="#performSave"/>
+                        <Button text="Reload Plugins" onAction="#performReload"/>
+                        <Button text="Apply and Reload" onAction="#performSaveAndReload"/>
+                        <Button text="Scan Plugins" onAction="#performScan"/>
+                    </FlowPane>
+                </GridPane>
+            </Tab>
+            <Tab fx:id="functionListTab" text="Functions" closable="false">
+                <VBox spacing="10">
+                    <padding>
+                        <Insets left="10" right="10" top="10" bottom="10"/>
+                    </padding>
+                    <TextField fx:id="functionListSearchField" maxWidth="Infinity"/>
+                    <ListView maxWidth="Infinity" fx:id="functionListView"/>
+                </VBox>
+            </Tab>
+        </TabPane>
+    </center>
+
+</BorderPane>

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

@@ -0,0 +1,107 @@
+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.NumberInterface;
+import org.nwapw.abacus.plugin.StandardPlugin;
+import org.nwapw.abacus.tree.TreeNode;
+
+public class CalculationTests {
+
+    private static Abacus abacus = new Abacus(new Configuration(0, "precise", new String[]{}));
+
+    @BeforeClass
+    public static void prepareTests(){
+        abacus.getPluginManager().addInstantiated(new StandardPlugin(abacus.getPluginManager()));
+        abacus.getPluginManager().load();
+    }
+
+    private void testOutput(String input, String parseOutput, String output){
+        TreeNode parsedTree = abacus.parseString(input);
+        Assert.assertNotNull(parsedTree);
+        Assert.assertEquals(parsedTree.toString(), parseOutput);
+        NumberInterface result = abacus.evaluateTree(parsedTree);
+        Assert.assertNotNull(result);
+        Assert.assertTrue(result.toString().startsWith(output));
+    }
+
+    private void testEvalError(String input, String parseOutput){
+        TreeNode parsedTree = abacus.parseString(input);
+        Assert.assertNotNull(parsedTree);
+        Assert.assertEquals(parsedTree.toString(), parseOutput);
+        Assert.assertNull(abacus.evaluateTree(parsedTree));
+    }
+
+    @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(){
+        testEvalError("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");
+        testEvalError("0^0", "(0^0)");
+        testEvalError("(-13)^.9999", "((13)`^0.9999)");
+    }
+
+}

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

@@ -0,0 +1,133 @@
+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 java.util.List;
+
+public class LexerTests {
+
+    @Test
+    public void testBasicSuccess() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("abc", 0);
+        lexer.register("def", 1);
+        List<Match<Integer>> matchedIntegers = lexer.lexAll("abcdefabc", 0, Integer::compare);
+        Assert.assertNotNull(matchedIntegers);
+        Assert.assertEquals(matchedIntegers.get(0).getType(), Integer.valueOf(0));
+        Assert.assertEquals(matchedIntegers.get(1).getType(), Integer.valueOf(1));
+        Assert.assertEquals(matchedIntegers.get(2).getType(), Integer.valueOf(0));
+    }
+
+    @Test
+    public void testBasicFailure() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("abc", 0);
+        lexer.register("def", 1);
+        Assert.assertNull(lexer.lexAll("abcdefabcz", 0, Integer::compare));
+    }
+
+    @Test
+    public void testNoPatterns() {
+        Lexer<Integer> lexer = new Lexer<>();
+        Assert.assertNull(lexer.lexAll("abcdefabc", 0, Integer::compare));
+    }
+
+    @Test
+    public void testEmptyMatches() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("a?", 0);
+        Assert.assertNull(lexer.lexAll("", 0, Integer::compare));
+    }
+
+    @Test
+    public void testOneOrMore() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("a+", 0);
+        List<Match<Integer>> tokens = lexer.lexAll("aaaa", 0, Integer::compare);
+        Assert.assertNotNull(tokens);
+        Assert.assertEquals(tokens.size(), 1);
+    }
+
+    @Test
+    public void testZeroOrMore() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("a*", 0);
+        List<Match<Integer>> tokens = lexer.lexAll("aaaa", 0, Integer::compare);
+        Assert.assertNotNull(tokens);
+        Assert.assertEquals(tokens.size(), 1);
+    }
+
+    @Test
+    public void testZeroOrOne() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("a?", 0);
+        List<Match<Integer>> tokens = lexer.lexAll("aaaa", 0, Integer::compare);
+        Assert.assertNotNull(tokens);
+        Assert.assertEquals(tokens.size(), 4);
+    }
+
+    @Test
+    public void testGreedyMatching() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("a*a", 0);
+        List<Match<Integer>> tokens = lexer.lexAll("aaaa", 0, Integer::compare);
+        Assert.assertNotNull(tokens);
+        Assert.assertEquals(tokens.size(), 1);
+    }
+
+    @Test
+    public void testAnyCharacter() {
+        String testString = "abcdef";
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register(".", 0);
+        List<Match<Integer>> tokens = lexer.lexAll(testString, 0, Integer::compare);
+        Assert.assertNotNull(tokens);
+        Assert.assertEquals(tokens.size(), testString.length());
+        for (int i = 0; i < tokens.size(); i++) {
+            Assert.assertEquals(testString.substring(i, i + 1), tokens.get(i).getContent());
+        }
+    }
+
+    @Test
+    public void testBasicGroup() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("(abc)", 0);
+        List<Match<Integer>> tokens = lexer.lexAll("abc", 0, Integer::compare);
+        Assert.assertNotNull(tokens);
+        Assert.assertEquals(tokens.size(), 1);
+        Assert.assertEquals(tokens.get(0).getContent(), "abc");
+    }
+
+    @Test
+    public void testBasicRangeSuccess() {
+        String testString = "abcdef";
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("[a-f]", 0);
+        List<Match<Integer>> tokens = lexer.lexAll(testString, 0, Integer::compare);
+        Assert.assertNotNull(tokens);
+        Assert.assertEquals(testString.length(), tokens.size());
+        for (int i = 0; i < tokens.size(); i++) {
+            Assert.assertEquals(testString.substring(i, i + 1), tokens.get(i).getContent());
+        }
+    }
+
+    @Test
+    public void testBasicRangeFailure() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("[a-f]", 0);
+        Assert.assertNull(lexer.lexAll("g", 0, Integer::compare));
+    }
+
+    @Test
+    public void testGroupAndOperator() {
+        Lexer<Integer> lexer = new Lexer<>();
+        lexer.register("(abc)+", 0);
+        List<Match<Integer>> tokens = lexer.lexAll("abcabc", 0, Integer::compare);
+        Assert.assertNotNull(tokens);
+        Assert.assertEquals(tokens.size(), 1);
+    }
+
+}

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

@@ -0,0 +1,125 @@
+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.function.Function;
+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.number.NumberInterface;
+import org.nwapw.abacus.parsing.LexerTokenizer;
+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(new Configuration(0, "precise", new String[]{}));
+    private static LexerTokenizer lexerTokenizer = new LexerTokenizer();
+    private static Function subtractFunction = new Function() {
+        @Override
+        protected boolean matchesParams(NumberInterface[] params) {
+            return params.length == 2;
+        }
+
+        @Override
+        protected NumberInterface applyInternal(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));
+            registerFunction("subtract", subtractFunction);
+        }
+
+        @Override
+        public void onDisable() {
+
+        }
+    };
+
+    private static void assertTokensMatch(List<Match<TokenType>> tokenList, TokenType[] expectedTypes) {
+        Assert.assertNotNull(tokenList);
+        Assert.assertEquals(tokenList.size(), expectedTypes.length);
+        for (int i = 0; i < expectedTypes.length; i++) {
+            Assert.assertEquals(expectedTypes[i], tokenList.get(i).getType());
+        }
+    }
+
+    @BeforeClass
+    public static void prepareTests() {
+        abacus.getPluginManager().addListener(lexerTokenizer);
+        abacus.getPluginManager().addInstantiated(testPlugin);
+        abacus.getPluginManager().load();
+    }
+
+    @Test
+    public void testInteger() {
+        assertTokensMatch(lexerTokenizer.tokenizeString("11"), new TokenType[]{TokenType.NUM});
+    }
+
+    @Test
+    public void testLeadingZeroDecimal() {
+        assertTokensMatch(lexerTokenizer.tokenizeString("0.1"), new TokenType[]{TokenType.NUM});
+    }
+
+    @Test
+    public void testNonLeadingDecimal() {
+        assertTokensMatch(lexerTokenizer.tokenizeString(".1"), new TokenType[]{TokenType.NUM});
+    }
+
+    @Test
+    public void testSimpleChars() {
+        TokenType[] types = {
+                TokenType.OPEN_PARENTH,
+                TokenType.WHITESPACE,
+                TokenType.COMMA,
+                TokenType.CLOSE_PARENTH
+        };
+        assertTokensMatch(lexerTokenizer.tokenizeString("( ,)"), types);
+    }
+
+    @Test
+    public void testFunctionParsing() {
+        TokenType[] types = {
+                TokenType.FUNCTION,
+                TokenType.OPEN_PARENTH,
+                TokenType.NUM,
+                TokenType.COMMA,
+                TokenType.NUM,
+                TokenType.CLOSE_PARENTH
+        };
+        assertTokensMatch(lexerTokenizer.tokenizeString("subtract(1,2)"), types);
+    }
+
+    @Test
+    public void testOperatorParsing() {
+        TokenType[] types = {
+                TokenType.NUM,
+                TokenType.OP,
+                TokenType.NUM
+        };
+        assertTokensMatch(lexerTokenizer.tokenizeString("1-1"), types);
+    }
+
+    @Test
+    public void testSanitizedOperators() {
+        TokenType[] types = {
+                TokenType.NUM,
+                TokenType.OP,
+                TokenType.NUM
+        };
+        assertTokensMatch(lexerTokenizer.tokenizeString("1+1"), types);
+    }
+
+}