Added support for assignable function results.

Also:
- Added megabuf(index) as a first, temporary example
- Introduced a new Node class at the top of the hierarchy for the runtime.
- RValue and LValue are now interfaces
- Narrowed down some exception declarations
- Optimized the optimizer for functions

src/main/java/com/sk89q/worldedit/expression/Identifiable.java

@@ -41,8 +41,9 @@ public interface Identifiable {
      *
      * Invokables:
      * c - Constant
-     * f - Function
      * v - Variable
+     * f - Function
+     * l - LValueFunction
      * </pre>
      */
     public abstract char id();

src/main/java/com/sk89q/worldedit/expression/runtime/Constant.java

@@ -24,7 +24,7 @@ package com.sk89q.worldedit.expression.runtime;
  *
  * @author TomyLobo
  */
-public final class Constant extends RValue {
+public final class Constant extends Node {
     private final double value;
 
     public Constant(int position, double value) {

src/main/java/com/sk89q/worldedit/expression/runtime/Function.java

@@ -29,7 +29,7 @@ import java.lang.reflect.Method;
  *
  * @author TomyLobo
  */
-public class Function extends RValue {
+public class Function extends Node {
     /**
      * Add this annotation on functions that don't always return the same value for the same inputs.
      */
@@ -47,8 +47,12 @@ public class Function extends RValue {
 
     @Override
     public final double getValue() throws EvaluationException {
+        return invokeMethod(method, args);
+    }
+
+    protected static final double invokeMethod(Method method, Object[] args) throws EvaluationException {
         try {
-            return (Double) method.invoke(null, (Object[]) args);
+            return (Double) method.invoke(null, args);
         } catch (InvocationTargetException e) {
             if (e.getTargetException() instanceof EvaluationException) {
                 throw (EvaluationException) e.getTargetException();
@@ -79,7 +83,7 @@ public class Function extends RValue {
     }
 
     @Override
-    public RValue optimize() throws EvaluationException {
+    public Node optimize() throws EvaluationException {
         final RValue[] optimizedArgs = new RValue[args.length];
         boolean optimizable = !method.isAnnotationPresent(Dynamic.class);
         int position = getPosition();
@@ -96,7 +100,9 @@ public class Function extends RValue {
         }
 
         if (optimizable) {
-            return new Constant(position, getValue());
+            return new Constant(position, invokeMethod(method, optimizedArgs));
+        } else if (this instanceof LValueFunction) {
+            return new LValueFunction(position, method, ((LValueFunction) this).setter, optimizedArgs);
         } else {
             return new Function(position, method, optimizedArgs);
         }

src/main/java/com/sk89q/worldedit/expression/runtime/Functions.java

@@ -25,6 +25,8 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import com.sk89q.worldedit.expression.runtime.Function.Dynamic;
+
 /**
  * Contains all functions that can be used in expressions.
  *
@@ -34,13 +36,24 @@ public final class Functions {
     private static class Overload {
         private final Method method; 
         private final int mask;
+        private final boolean isSetter;
 
         public Overload(Method method) throws IllegalArgumentException {
             this.method = method;
 
+            boolean isSetter = false;
             int accum = 0;
             Class<?>[] parameters = method.getParameterTypes();
             for (Class<?> parameter : parameters) {
+                if (isSetter) {
+                    throw new IllegalArgumentException("Method takes arguments that can't be cast to RValue.");
+                }
+
+                if (double.class.equals(parameter)) {
+                    isSetter = true;
+                    continue;
+                }
+
                 if (!RValue.class.isAssignableFrom(parameter)) {
                     throw new IllegalArgumentException("Method takes arguments that can't be cast to RValue.");
                 }
@@ -54,9 +67,14 @@ public final class Functions {
                 }
             }
             mask = accum;
+            this.isSetter = isSetter;
         }
 
-        public boolean matches(RValue... args) {
+        public boolean matches(boolean isSetter, RValue... args) {
+            if (this.isSetter != isSetter) {
+                return false;
+            }
+
             int accum = 0;
             for (RValue argument : args) {
                 accum <<= 2;
@@ -74,14 +92,21 @@ public final class Functions {
 
 
     public static final Function getFunction(int position, String name, RValue... args) throws NoSuchMethodException {
-        return new Function(position, getMethod(name, args), args);
+        final Method getter = getMethod(name, false, args);
+        try {
+            Method setter = getMethod(name, true, args);
+            return new LValueFunction(position, getter, setter, args);
+        }
+        catch (NoSuchMethodException e) {
+            return new Function(position, getter, args);
+        }
     }
 
-    private static Method getMethod(String name, RValue... args) throws NoSuchMethodException {
+    private static Method getMethod(String name, boolean isSetter, RValue... args) throws NoSuchMethodException {
         final List<Overload> overloads = functions.get(name);
         if (overloads != null) {
             for (Overload overload : overloads) {
-                if (overload.matches(args)) {
+                if (overload.matches(isSetter, args)) {
                     return overload.method;
                 }
             }
@@ -93,125 +118,130 @@ public final class Functions {
     private static final Map<String, List<Overload>> functions = new HashMap<String, List<Overload>>();
     static {
         for (Method method : Functions.class.getMethods()) {
-            final String methodName = method.getName();
-
             try {
-                Overload overload = new Overload(method);
-
-                List<Overload> overloads = functions.get(methodName);
-                if (overloads == null) {
-                    functions.put(methodName, overloads = new ArrayList<Overload>());
-                }
-
-                overloads.add(overload);
+                addFunction(method);
             } catch(IllegalArgumentException e) {}
         }
     }
 
 
-    public static final double sin(RValue x) throws Exception {
+    public static void addFunction(Method method) throws IllegalArgumentException {
+        final String methodName = method.getName();
+
+        Overload overload = new Overload(method);
+
+        List<Overload> overloads = functions.get(methodName);
+        if (overloads == null) {
+            functions.put(methodName, overloads = new ArrayList<Overload>());
+        }
+
+        overloads.add(overload);
+    }
+
+
+    public static final double sin(RValue x) throws EvaluationException {
         return Math.sin(x.getValue());
     }
 
-    public static final double cos(RValue x) throws Exception {
+    public static final double cos(RValue x) throws EvaluationException {
         return Math.cos(x.getValue());
     }
 
-    public static final double tan(RValue x) throws Exception {
+    public static final double tan(RValue x) throws EvaluationException {
         return Math.tan(x.getValue());
     }
 
 
-    public static final double asin(RValue x) throws Exception {
+    public static final double asin(RValue x) throws EvaluationException {
         return Math.asin(x.getValue());
     }
 
-    public static final double acos(RValue x) throws Exception {
+    public static final double acos(RValue x) throws EvaluationException {
         return Math.acos(x.getValue());
     }
 
-    public static final double atan(RValue x) throws Exception {
+    public static final double atan(RValue x) throws EvaluationException {
         return Math.atan(x.getValue());
     }
 
-    public static final double atan2(RValue y, RValue x) throws Exception {
+    public static final double atan2(RValue y, RValue x) throws EvaluationException {
         return Math.atan2(y.getValue(), x.getValue());
     }
 
 
-    public static final double sinh(RValue x) throws Exception {
+    public static final double sinh(RValue x) throws EvaluationException {
         return Math.sinh(x.getValue());
     }
 
-    public static final double cosh(RValue x) throws Exception {
+    public static final double cosh(RValue x) throws EvaluationException {
         return Math.cosh(x.getValue());
     }
 
-    public static final double tanh(RValue x) throws Exception {
+    public static final double tanh(RValue x) throws EvaluationException {
         return Math.tanh(x.getValue());
     }
 
 
-    public static final double sqrt(RValue x) throws Exception {
+    public static final double sqrt(RValue x) throws EvaluationException {
         return Math.sqrt(x.getValue());
     }
 
-    public static final double cbrt(RValue x) throws Exception {
+    public static final double cbrt(RValue x) throws EvaluationException {
         return Math.cbrt(x.getValue());
     }
 
 
-    public static final double abs(RValue x) throws Exception {
+    public static final double abs(RValue x) throws EvaluationException {
         return Math.abs(x.getValue());
     }
 
-    public static final double min(RValue a, RValue b) throws Exception {
+    public static final double min(RValue a, RValue b) throws EvaluationException {
         return Math.min(a.getValue(), b.getValue());
     }
 
-    public static final double min(RValue a, RValue b, RValue c) throws Exception {
+    public static final double min(RValue a, RValue b, RValue c) throws EvaluationException {
         return Math.min(a.getValue(), Math.min(b.getValue(), c.getValue()));
     }
 
-    public static final double max(RValue a, RValue b) throws Exception {
+    public static final double max(RValue a, RValue b) throws EvaluationException {
         return Math.max(a.getValue(), b.getValue());
     }
 
-    public static final double max(RValue a, RValue b, RValue c) throws Exception {
+    public static final double max(RValue a, RValue b, RValue c) throws EvaluationException {
         return Math.max(a.getValue(), Math.max(b.getValue(), c.getValue()));
     }
 
 
-    public static final double ceil(RValue x) throws Exception {
+    public static final double ceil(RValue x) throws EvaluationException {
         return Math.ceil(x.getValue());
     }
 
-    public static final double floor(RValue x) throws Exception {
+    public static final double floor(RValue x) throws EvaluationException {
         return Math.floor(x.getValue());
     }
 
-    public static final double rint(RValue x) throws Exception {
+    public static final double rint(RValue x) throws EvaluationException {
         return Math.rint(x.getValue());
     }
 
-    public static final double round(RValue x) throws Exception {
+    public static final double round(RValue x) throws EvaluationException {
         return Math.round(x.getValue());
     }
 
 
-    public static final double exp(RValue x) throws Exception {
+    public static final double exp(RValue x) throws EvaluationException {
         return Math.exp(x.getValue());
     }
 
-    public static final double ln(RValue x) throws Exception {
+    public static final double ln(RValue x) throws EvaluationException {
         return Math.log(x.getValue());
     }
 
-    public static final double log(RValue x) throws Exception {
+    public static final double log(RValue x) throws EvaluationException {
         return Math.log(x.getValue());
     }
 
-    public static final double log10(RValue x) throws Exception {
+    public static final double log10(RValue x) throws EvaluationException {
         return Math.log10(x.getValue());
     }
 
@@ -230,4 +260,17 @@ public final class Functions {
 
         return 0;
     }
+
+
+    private static final double[] megabuf = new double[1024];
+
+    @Dynamic
+    public static final double megabuf(RValue index) throws EvaluationException {
+        return megabuf[(int) index.getValue()];
+    }
+
+    @Dynamic
+    public static final double megabuf(RValue index, double value) throws EvaluationException {
+        return megabuf[(int) index.getValue()] = value;
+    }
 }

src/main/java/com/sk89q/worldedit/expression/runtime/LValue.java

@@ -24,10 +24,6 @@ package com.sk89q.worldedit.expression.runtime;
  *
  * @author TomyLobo
  */
-public abstract class LValue extends RValue {
-    public LValue(int position) {
-        super(position);
-    }
-
-    public abstract double assign(double value) throws EvaluationException;
+public interface LValue extends RValue {
+    public double assign(double value) throws EvaluationException;
 }

src/main/java/com/sk89q/worldedit/expression/runtime/LValueFunction.java

@@ -0,0 +1,51 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010, 2011 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.expression.runtime;
+
+import java.lang.reflect.Method;
+
+/**
+ * Wrapper for a Java method and its arguments (other Invokables)
+ *
+ * @author TomyLobo
+ */
+public class LValueFunction extends Function implements LValue {
+    private final Object[] setterArgs;
+    final Method setter;
+
+    LValueFunction(int position, Method getter, Method setter, RValue... args) {
+        super(position, getter, args);
+
+        setterArgs = new Object[args.length + 1];
+        System.arraycopy(args, 0, setterArgs, 0, args.length);
+        this.setter = setter;
+    }
+
+    @Override
+    public char id() {
+        return 'l';
+    }
+
+    @Override
+    public double assign(double value) throws EvaluationException {
+        setterArgs[setterArgs.length - 1] = value;
+        return invokeMethod(setter, setterArgs);
+    }
+}

src/main/java/com/sk89q/worldedit/expression/runtime/Node.java

@@ -0,0 +1,45 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010, 2011 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.expression.runtime;
+
+/**
+ * A value that can be used on the right side of an assignment.
+ *
+ * @author TomyLobo
+ */
+public abstract class Node implements RValue {
+    private final int position;
+
+    public Node(int position) {
+        this.position = position;
+    }
+
+    @Override
+    public abstract String toString();
+
+    public Node optimize() throws EvaluationException {
+        return this;
+    }
+
+    @Override
+    public int getPosition() {
+        return position;
+    }
+}

src/main/java/com/sk89q/worldedit/expression/runtime/RValue.java

@@ -26,25 +26,7 @@ import com.sk89q.worldedit.expression.Identifiable;
  *
  * @author TomyLobo
  */
-public abstract class RValue implements Identifiable {
-    private final int position;
-
-    public RValue(int position) {
-        super();
-        this.position = position;
-    }
-
-    public abstract double getValue() throws EvaluationException;
-
-    @Override
-    public abstract String toString();
-
-    public RValue optimize() throws EvaluationException {
-        return this;
-    }
-
-    @Override
-    public int getPosition() {
-        return position;
-    }
+public interface RValue extends Identifiable {
+    public double getValue() throws EvaluationException;
+    public Node optimize() throws EvaluationException;
 }

src/main/java/com/sk89q/worldedit/expression/runtime/Sequence.java

@@ -27,7 +27,7 @@ import java.util.List;
  *
  * @author TomyLobo
  */
-public class Sequence extends RValue {
+public class Sequence extends Node {
     private final RValue[] sequence;
 
     public Sequence(int position, RValue... sequence) {
@@ -66,7 +66,7 @@ public class Sequence extends RValue {
     }
 
     @Override
-    public RValue optimize() throws EvaluationException {
+    public Node optimize() throws EvaluationException {
         List<RValue> newSequence = new ArrayList<RValue>();
 
         for (RValue invokable : sequence) {

src/main/java/com/sk89q/worldedit/expression/runtime/Variable.java

@@ -24,7 +24,7 @@ package com.sk89q.worldedit.expression.runtime;
  *
  * @author TomyLobo
  */
-public final class Variable extends LValue {
+public final class Variable extends Node implements LValue {
     public double value;
 
     public Variable(double value) {