飞镖比较运算符 [英] Dart comparison operators

问题描述

我正在研究一个用于度量的类，所以我想提供一个不错的API来比较两个度量。

为了处理集合中的订购，我实现了比较器。对于一个不错的API，我还实现了比较运算符< ，< = ， = > ，> ， == 。

所以我的课有以下方法：

 布尔运算符< =（SELF other）=> _value< = other._value; 
 
布尔运算符<（SELF other）=> _value< other._value; 
 
布尔运算符>（SELF other）=> _value> other._value; 
 
 bool运算符> =（SELF other）=> _value> = other._value; 
 
 @override 
布尔运算符==（其他对象）=> 
 same（this，other）||另一个是UnitValue&& runtimeType == other.runtimeType& _value == other._value; 
 
 @override 
 int get hashCode => _value.hashCode; 
 
 int compareTo（SELF other）=> _value.compareTo（other._value）; 
  

感觉就像我不得不添加太多样板代码。 Dart是否会为基于操作符子集的所有实现提供任何混合方式？

解决方案

我不这么认为。 ，但您可以基于 Comparable 实现使用简单的混合函数来实现运算符：

  mixin Compare< T>在可比较的< T>上{
 bool运算符< =（Tother）=> this.compareTo（other）< = 0; 
 
布尔运算符> =（Tother）=> this.compareTo（other）> = 0; 
 
个布尔运算符<（Tother）=> this.compareTo（other）< 0; 
 
布尔运算符>（Tother）=> this.compareTo（other）> 0; 
 
布尔运算符==（other）=>其他是T&& this.compareTo（other）== 0; 
} 
  

示例用法：

<具有可比较< Vec> ;、比较< Vec>的pre> 类Vec。 {
最终双倍x；
最终双倍y；

Vec（this.x，this.y）;

@override
int compareTo（Vec other）=>
（x.abs（）+ y.abs（））。compareTo（other.x.abs（）+ other.y.abs（））;
}

main（）{
print（Vec（1，1）> Vec（0，0））;
print（Vec（1，0）> Vec（0，0））;
print（Vec（0，0）== Vec（0，0））;
print（Vec（1，1）< = Vec（2，0））;
}


I work on a class for measurements, so I would like to provide a nice API to compare two measurements.

In order to work with ordering in collection I implemented Comparator. For a nice API I implemented as well comparing operators <, <=, =>, >, ==.

So my class has the following methods:

bool operator <=(SELF other) => _value <= other._value;

bool operator <(SELF other) => _value < other._value;

bool operator >(SELF other) => _value > other._value;

bool operator >=(SELF other) => _value >= other._value;

@override
bool operator ==(Object other) =>
    identical(this, other) || other is UnitValue && runtimeType == other.runtimeType && _value == other._value;

@override
int get hashCode => _value.hashCode;

int compareTo(SELF other) => _value.compareTo(other._value);

It feels like I had to add way too much boilerplate code. Does Dart provide any mixing for getting all that implementation based on a subset of operators?

解决方案

I don't think so... but you can use a simple mixin for implementing operators based on the Comparable implementation:

mixin Compare<T> on Comparable<T> {
  bool operator <=(T other) => this.compareTo(other) <= 0;

  bool operator >=(T other) => this.compareTo(other) >= 0;

  bool operator <(T other) => this.compareTo(other) < 0;

  bool operator >(T other) => this.compareTo(other) > 0;

  bool operator ==(other) => other is T && this.compareTo(other) == 0;
}

Example usage:

class Vec with Comparable<Vec>, Compare<Vec> {
  final double x;
  final double y;

  Vec(this.x, this.y);

  @override
  int compareTo(Vec other) =>
      (x.abs() + y.abs()).compareTo(other.x.abs() + other.y.abs());
}

main() {
  print(Vec(1, 1) > Vec(0, 0));
  print(Vec(1, 0) > Vec(0, 0));
  print(Vec(0, 0) == Vec(0, 0));
  print(Vec(1, 1) <= Vec(2, 0));
}

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