dart / sdk.git / 37da58cbbc164ac17e371cc1c63d0c3364e33b6e / . / tests / language / operator / round_test.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. | |

/// Test of a common rounding bug. | |

/// | |

/// This bug is common in JavaScript implementations because the ECMA-262 | |

/// specification of JavaScript incorrectly claims: | |

/// | |

/// The value of [:Math.round(x):] is the same as the value of | |

/// [:Math.floor(x+0.5):], except when x is 0 or is less than 0 but greater | |

/// than or equal to -0.5; for these cases [:Math.round(x):] returns 0, but | |

/// [:Math.floor(x+0.5):] returns +0. | |

/// | |

/// However, 0.49999999999999994 + 0.5 is 1 and 9007199254740991 + 0.5 is | |

/// 9007199254740992, so you cannot implement Math.round in terms of | |

/// Math.floor. | |

import 'package:expect/expect.dart'; | |

main() { | |

Expect.equals(0, (0.49999999999999994).round()); | |

Expect.equals(0, (-0.49999999999999994).round()); | |

Expect.equals(9007199254740991, (9007199254740991.0).round()); | |

Expect.equals(-9007199254740991, (-9007199254740991.0).round()); | |

} |