IEqualityComparer <double>具有容差; 如何实现GetHashCode？

Question

我正在实现一个可重用的DoubleEqualityComparer(具有自定义容差:"epsilon"构造函数参数),以简化LINQ的使用,使用double序列.例如:

bool myDoubleFound = doubles.Contains(myDouble, new DoubleEqualityComparer(epsilon: 0.01));

实现GetHashCode的正确方法是什么？这是代码:

   public class DoubleEqualityComparer : IEqualityComparer<double>, IEqualityComparer<double?>
    {
        private readonly double epsilon;

        public DoubleEqualityComparer(double epsilon)
        {
            if (epsilon < 0)
            {
                throw new ArgumentException("epsilon can't be negative", "epsilon");
            }

            this.epsilon = epsilon;
        }

        public bool Equals(double x, double y)
        {
            return System.Math.Abs(x - y) < this.epsilon;
        }

        public int GetHashCode(double obj)
        {
            // ?
        }
   }

PS:我总是可以返回相同的值(例如:GetHashCode(double obj){return 0;})以始终强制调用Equals(double,double)方法(不是很高效,我知道),但我记得这个当比较器与字典一起使用时,解决方案会导致问题...

Answer 1

我不确定使用EqualityComparer是否可行.因为比较的对象不等于.

也许你应该考虑使用一个简单的Any子句+一个实用的方法:

private static bool DoublesAreNearlyEquals(double d1, double d2, double epsilon = 0.01D)
{
    return System.Math.Abs(d1 - d2) < this.epsilon;
}

private void foo()
{
    var myDoubles = Getdoubles();
    var doubleToSearch = 42D;
    var result = myDoubles.Any(d=>DoublesAreNearlyEquals(d, doubleToSearch));
}