Ternary operator support for polymer_expressions

pkg/polymer_expressions/lib/eval.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library polymer_expressions.eval;
 
 import 'dart:async';
 import 'dart:collection';
 
 @MirrorsUsed(metaTargets: const [Reflectable, ObservableProperty],
@@ skipping 352 matching lines @@
     return binary;
   }
 
   visitUnaryOperator(UnaryOperator o) {
     var expr = visit(o.child);
     var unary = new UnaryObserver(o, expr);
     expr._parent = unary;
     return unary;
   }
 
+  visitTernaryOperator(TernaryOperator o) {
+    var condition = visit(o.condition);
+    var trueExpr = visit(o.trueExpr);
+    var falseExpr = visit(o.falseExpr);
+    var ternary = new TernaryObserver(o, condition, trueExpr, falseExpr);
+    condition._parent = ternary;
+    trueExpr._parent = ternary;
+    falseExpr._parent = ternary;
+    return ternary;
+  }
+
   visitInExpression(InExpression i) {
     // don't visit the left. It's an identifier, but we don't want to evaluate
     // it, we just want to add it to the comprehension object
     var left = visit(i.left);
     var right = visit(i.right);
     var inexpr = new InObserver(i, left, right);
     right._parent = inexpr;
     return inexpr;
   }
 }
@@ skipping 135 matching lines @@
             .listen((_) => _invalidate(scope));
       }
       _value = f(left._value, right._value);
     }
   }
 
   accept(Visitor v) => v.visitBinaryOperator(this);
 
 }
 
+class TernaryObserver extends ExpressionObserver<TernaryOperator>
+    implements TernaryOperator {
+
+  final ExpressionObserver condition;
+  final ExpressionObserver trueExpr;
+  final ExpressionObserver falseExpr;
+
+  TernaryObserver(TernaryOperator expr, this.condition, this.trueExpr,
+      this.falseExpr) : super(expr);
+
+  _updateSelf(Scope scope) {
+    _value = _toBool(condition._value) ? trueExpr._value : falseExpr._value;
+  }
+
+  accept(Visitor v) => v.visitTernaryOperator(this);
+
+}
+
 class GetterObserver extends ExpressionObserver<Getter> implements Getter {
   final ExpressionObserver receiver;
 
   GetterObserver(Expression expr, this.receiver) : super(expr);
 
   String get name => _expr.name;
 
   _updateSelf(Scope scope) {
     var receiverValue = receiver._value;
     if (receiverValue == null) {
@@ skipping 155 matching lines @@
    * This does not work for calls that need to pass more than one argument.
    */
   call(arg0) => mirror.invoke(symbol, [arg0], null).reflectee;
 }
 
 class EvalException implements Exception {
   final String message;
   EvalException(this.message);
   String toString() => "EvalException: $message";
 }