Move the source files into a new default directory.

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;
+    }
+
+}