Expression parser improvements

- Fixed calling nullary functions.
- Improved error reporting for missing functions
- Added random() and randint(max)
- Improved Sequence.optimize() to eliminate statements with no effect
- Adjusted a comment

src/main/java/com/sk89q/worldedit/expression/parser/Parser.java

@@ -351,6 +351,7 @@ public class Parser {
 
         try {
             if (peek().id() == ')') {
+                ++position;
                 return Functions.getFunction(identifierToken.getPosition(), identifierToken.value);
             }
 
@@ -376,7 +377,7 @@ public class Parser {
 
             return Functions.getFunction(identifierToken.getPosition(), identifierToken.value, args.toArray(new RValue[args.size()]));
         } catch (NoSuchMethodException e) {
-            throw new ParserException(identifierToken.getPosition(), "Function not found", e);
+            throw new ParserException(identifierToken.getPosition(), "Function '"+identifierToken.value+"' not found", e);
         }
     }
 

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

@@ -31,7 +31,8 @@ import java.lang.reflect.Method;
  */
 public class Function extends Node {
     /**
-     * Add this annotation on functions that don't always return the same value for the same inputs.
+     * Add this annotation on functions that don't always return the same value
+     * for the same inputs and on functions with side-effects.
      */
     @Retention(RetentionPolicy.RUNTIME)
     public @interface Dynamic { }

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

@@ -24,6 +24,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Random;
 
 import com.sk89q.worldedit.expression.runtime.Function.Dynamic;
 
@@ -281,4 +282,17 @@ public final class Functions {
         final int intIndex = (int) index.getValue();
         return getSubBuffer(intIndex & ~1023)[intIndex & 1023] = value;
     }
+
+
+    private static final Random random = new Random();
+
+    @Dynamic
+    public static final double random() {
+        return random.nextDouble();
+    }
+
+    @Dynamic
+    public static final double randint(RValue max) throws EvaluationException {
+        return random.nextInt((int) Math.floor(max.getValue()));
+    }
 }

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

@@ -69,17 +69,25 @@ public class Sequence extends Node {
     public Node optimize() throws EvaluationException {
         List<RValue> newSequence = new ArrayList<RValue>();
 
+        RValue droppedLast = null;
         for (RValue invokable : sequence) {
+            droppedLast = null;
             invokable = invokable.optimize();
             if (invokable instanceof Sequence) {
                 for (RValue subInvokable : ((Sequence) invokable).sequence) {
                     newSequence.add(subInvokable);
                 }
+            } else if (invokable instanceof Constant) {
+                droppedLast = invokable;
             } else {
                 newSequence.add(invokable);
             }
         }
 
+        if (droppedLast != null) {
+            newSequence.add(droppedLast);
+        }
+
         return new Sequence(getPosition(), newSequence.toArray(new RValue[newSequence.size()]));
     }
 }