Allow constant folding of && and ||.

frog/leg/operations.dart

Index: frog/leg/operations.dart
diff --git a/frog/leg/operations.dart b/frog/leg/operations.dart
index 0f5ea51f6da5595c823b0b0c52191e0a2d913875..11304ddf7660231a076829a61184ea2d54795c10 100644
--- a/frog/leg/operations.dart
+++ b/frog/leg/operations.dart
@@ -105,6 +105,32 @@ class ShiftRightOperation extends BinaryIntOperation {
   }
 }
 
+class BinaryBoolOperation implements BinaryOperation {
+  const BinaryBoolOperation();
+  Constant fold(Constant left, Constant right) {
+    if (left.isBool() && right.isBool()) {
+      BoolConstant leftBool = left;
+      BoolConstant rightBool = right;
+      bool resultValue = foldBools(leftBool.value, rightBool.value);
+      if (resultValue === null) return null;

[ngeoffray, 2012/03/26 13:19:09]

I believe this can never be true.

[karlklose, 2012/03/26 13:24:52]

Not in the current subclasses, that is correct. I will remove it.

+      return new BoolConstant(resultValue);
+    }
+    return null;
+  }
+
+  abstract bool foldBools(bool left, bool right);
+}
+
+class BooleanAnd extends BinaryBoolOperation {
+  const BooleanAnd();
+  bool foldBools(bool left, bool right) => left && right;
+}
+
+class BooleanOr extends BinaryBoolOperation {
+  const BooleanOr();
+  bool foldBools(bool left, bool right) => left || right;
+}
+
 class ArithmeticNumOperation implements BinaryOperation {
   const ArithmeticNumOperation();
   Constant fold(Constant left, Constant right) {