Language/Classes/Instance_Methods/Operators/arity_0_or_1_t01.dart

// Copyright (c) 2011, 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.

/**
 * @assertion  It is a compile-time error if the arity of the user-declared
 * operator - is not 0 or 1.
 * The - operator is unique in that two overloaded versions are permitted.
 * If the operator has no arguments, it denotes unary minus.
 * If it as an argument, it denotes binary subtraction.
 * @description Checks that operator - can be defined both with 0 and 1 
 * arguments.
 * @author kaigorodov
 */
import "../../../../Utils/expect.dart";

class C {
  bool v;
  C(this.v);
  operator -() {
    return !v;
  }

  operator -(C v2) {
    return v || !v2.v;
  }
}

main() {
  Expect.isTrue(-new C(false));
  Expect.isTrue(new C(true) - new C(false));
  Expect.isFalse(new C(false) - new C(true));
}