Move the source files into a new default directory.

src/main/java/org/nwapw/abacus/tree/BinaryInfixNode.java

@@ -0,0 +1,100 @@
+package org.nwapw.abacus.tree;
+
+/**
+ * A tree node that represents an operation being applied to two operands.
+ */
+public class BinaryInfixNode extends TreeNode {
+
+    /**
+     * The operation being applied.
+     */
+    private String operation;
+    /**
+     * The left node of the operation.
+     */
+    private TreeNode left;
+    /**
+     * The right node of the operation.
+     */
+    private TreeNode right;
+
+    private BinaryInfixNode() {}
+
+    /**
+     * Creates a new operation node with the given operation
+     * and no child nodes.
+     * @param operation the operation.
+     */
+    public BinaryInfixNode(String operation){
+        this(operation, null, null);
+    }
+
+    /**
+     * Creates a new operation node with the given operation
+     * and child nodes.
+     * @param operation the operation.
+     * @param left the left node of the expression.
+     * @param right the right node of the expression.
+     */
+    public BinaryInfixNode(String operation, TreeNode left, TreeNode right){
+        this.operation = operation;
+        this.left = left;
+        this.right = right;
+    }
+
+    /**
+     * Gets the operation in this node.
+     * @return the operation in this node.
+     */
+    public String getOperation() {
+        return operation;
+    }
+
+    /**
+     * Gets the left sub-expression of this node.
+     * @return the left node.
+     */
+    public TreeNode getLeft() {
+        return left;
+    }
+
+    /**
+     * Sets the left sub-expression of this node.
+     * @param left the sub-expression to apply.
+     */
+    public void setLeft(TreeNode left) {
+        this.left = left;
+    }
+
+    /**
+     * Gets the right sub-expression of this node.
+     * @return the right node.
+     */
+    public TreeNode getRight() {
+        return right;
+    }
+
+    /**
+     * Sets the right sub-expression of this node.
+     * @param right the sub-expression to apply.
+     */
+    public void setRight(TreeNode right) {
+        this.right = right;
+    }
+
+    @Override
+    public <T> T reduce(Reducer<T> reducer) {
+        T leftReduce = left.reduce(reducer);
+        T rightReduce = right.reduce(reducer);
+        if(leftReduce == null || rightReduce == null) return null;
+        return reducer.reduceNode(this, leftReduce, rightReduce);
+    }
+
+    @Override
+    public String toString() {
+        String leftString = left != null ? left.toString() : "null";
+        String rightString = right != null ? right.toString() : "null";
+
+        return "(" + leftString + operation + rightString + ")";
+    }
+}

src/main/java/org/nwapw/abacus/tree/FunctionNode.java

@@ -0,0 +1,80 @@
+package org.nwapw.abacus.tree;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A node that represents a function call.
+ */
+public class FunctionNode extends TreeNode {
+
+    /**
+     * The name of the function being called
+     */
+    private String function;
+    /**
+     * The list of arguments to the function.
+     */
+    private List<TreeNode> children;
+
+    /**
+     * Creates a function node with no function.
+     */
+    private FunctionNode() { }
+
+    /**
+     * Creates a new function node with the given function name.
+     * @param function the function name.
+     */
+    public FunctionNode(String function){
+        this.function = function;
+        children = new ArrayList<>();
+    }
+
+    /**
+     * Gets the function name for this node.
+     * @return the function name.
+     */
+    public String getFunction() {
+        return function;
+    }
+
+    /**
+     * Adds a child to the end of this node's child list.
+     * @param node the child to add.
+     */
+    public void appendChild(TreeNode node){
+        children.add(node);
+    }
+
+    /**
+     * Adds a new child to the beginning of this node's child list.
+     * @param node the node to add.
+     */
+    public void prependChild(TreeNode node) {
+        children.add(0, node);
+    }
+
+    @Override
+    public <T> T reduce(Reducer<T> reducer) {
+        Object[] reducedChildren = new Object[children.size()];
+        for(int i = 0; i < reducedChildren.length; i++){
+            reducedChildren[i] = children.get(i).reduce(reducer);
+            if(reducedChildren[i] == null) return null;
+        }
+        return reducer.reduceNode(this, reducedChildren);
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder buffer = new StringBuilder();
+        buffer.append(function);
+        buffer.append("(");
+        for(int i = 0; i < children.size(); i++){
+            buffer.append(children.get(i));
+            buffer.append(i == children.size() - 1 ? "" : ", ");
+        }
+        buffer.append(")");
+        return buffer.toString();
+    }
+}

src/main/java/org/nwapw/abacus/tree/NumberNode.java

@@ -0,0 +1,48 @@
+package org.nwapw.abacus.tree;
+
+import org.nwapw.abacus.number.NaiveNumber;
+import org.nwapw.abacus.number.NumberInterface;
+
+/**
+ * A node implementation that represents a single number.
+ */
+public class NumberNode extends TreeNode {
+
+    /**
+     * The number that is represented by this number node.
+     */
+    private NumberInterface number;
+
+    /**
+     * Creates a number node with no number.
+     */
+    public NumberNode(){
+        number = null;
+    }
+
+    /**
+     * Creates a new number node with the given double value.
+     * @param newNumber the number for which to create a number node.
+     */
+    public NumberNode(NumberInterface newNumber){
+        this.number = newNumber;
+    }
+
+    /**
+     * Gets the number value of this node.
+     * @return the number value of this node.
+     */
+    public NumberInterface getNumber() {
+        return number;
+    }
+
+    @Override
+    public <T> T reduce(Reducer<T> reducer) {
+        return reducer.reduceNode(this);
+    }
+
+    @Override
+    public String toString() {
+        return number != null ? number.toString() : "null";
+    }
+}

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

@@ -0,0 +1,53 @@
+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 BinaryInfixNode){
+            NumberInterface left = (NumberInterface) children[0];
+            NumberInterface right = (NumberInterface) children[1];
+            Function function = abacus.getPluginManager().operatorFor(((BinaryInfixNode) node).getOperation()).getFunction();
+            if(function == null) return null;
+            return function.apply(left, right);
+        } else if(node instanceof UnaryPrefixNode) {
+            NumberInterface child = (NumberInterface) children[0];
+            Function functionn = abacus.getPluginManager().operatorFor(((UnaryPrefixNode) 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;
+    }
+
+}

src/main/java/org/nwapw/abacus/tree/Reducer.java

@@ -0,0 +1,17 @@
+package org.nwapw.abacus.tree;
+
+/**
+ * Interface used to reduce a tree into a single value.
+ * @param <T> the value to reduce into.
+ */
+public interface Reducer<T> {
+
+    /**
+     * Reduces the given tree into a single value of type T.
+     * @param node the node being passed in to be reduced.
+     * @param children the already-reduced children of this node.
+     * @return the resulting value from the reduce.
+     */
+    public T reduceNode(TreeNode node, Object...children);
+
+}

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

@@ -0,0 +1,25 @@
+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;
+    }
+
+}

src/main/java/org/nwapw/abacus/tree/TreeNode.java

@@ -0,0 +1,22 @@
+package org.nwapw.abacus.tree;
+
+import org.nwapw.abacus.function.OperatorAssociativity;
+import org.nwapw.abacus.lexing.Lexer;
+import org.nwapw.abacus.lexing.pattern.Match;
+
+import java.util.*;
+
+/**
+ * An abstract class that represents an expression tree node.
+ */
+public abstract class TreeNode {
+
+    /**
+     * The function that reduces a tree to a single vale.
+     * @param reducer the reducer used to reduce the tree.
+     * @param <T> the type the reducer produces.
+     * @return the result of the reduction, or null on error.
+     */
+    public abstract <T> T reduce(Reducer<T> reducer);
+
+}

src/main/java/org/nwapw/abacus/tree/UnaryPrefixNode.java

@@ -0,0 +1,59 @@
+package org.nwapw.abacus.tree;
+
+public class UnaryPrefixNode extends TreeNode {
+
+    /**
+     * The operation this node will apply.
+     */
+    private String operation;
+    /**
+     * The tree node to apply the operation to.
+     */
+    private TreeNode applyTo;
+
+    /**
+     * Creates a new node with the given operation and no child.
+     * @param operation the operation for this node.
+     */
+    public UnaryPrefixNode(String operation){
+        this(operation, null);
+    }
+
+    /**
+     * Creates a new node with the given operation and child.
+     * @param operation the operation for this node.
+     * @param applyTo the node to apply the function to.
+     */
+    public UnaryPrefixNode(String operation, TreeNode applyTo){
+        this.operation = operation;
+        this.applyTo = applyTo;
+    }
+
+    @Override
+    public <T> T reduce(Reducer<T> reducer) {
+        Object reducedChild = applyTo.reduce(reducer);
+        if(reducedChild == null) return null;
+        return reducer.reduceNode(this, reducedChild);
+    }
+
+    /**
+     * Gets the operation of this node.
+     * @return the operation this node performs.
+     */
+    public String getOperation() {
+        return operation;
+    }
+
+    /**
+     * Gets the node to which this node's operation applies.
+     * @return the tree node to which the operation will be applied.
+     */
+    public TreeNode getApplyTo() {
+        return applyTo;
+    }
+
+    @Override
+    public String toString() {
+        return "(" + (applyTo == null ? "null" : applyTo.toString()) + ")" + operation;
+    }
+}