检查List< float>中的float时的C#精度与包含方法 [英] C# accuracy when checking float in List<float> with Contains method

问题描述

我有一个 float 的列表，并想通过 List.Contains()方法检查它是否已经包含特定值.我知道，对于 float 相等性测试，您通常不能使用 == ，但是类似 myFloat-value<0.001 .

I have a list of floats and want to check if it already contains a particular value with the List.Contains() method. I know that for float equality tests you often can't use == but something like myFloat - value < 0.001.

我的问题是，是 Contains 方法解决这个问题还是我需要使用一种方法来解决 float 精度错误，以便测试浮点数是否在列表吗?

My question is, does the Contains method account for this or I do I need to use a method that accounts for float precision errors for testing if the float is in the list?

推荐答案

从

此方法通过使用默认的相等比较器来确定相等，该比较器由对象的

This method determines equality by using the default equality comparer, as defined by the object's implementation of the IEquatable<T>.Equals method for T (the type of values in the list).

因此，您将需要自己处理与阈值的比较.例如，您可以使用自己的自定义相等比较器.像这样:

So you will need to handle comparison with a threshold yourself. For example, you can use your own custom equality comparer. Something like this:

public class FloatThresholdComparer : IEqualityComparer<float>
{
    private readonly float _threshold;
    public FloatThresholdComparer(float threshold)
    {
        _threshold = threshold;
    }

    public bool Equals(float x, float y)
    {
        return Math.Abs(x-y) < _threshold;
    }

    public int GetHashCode(float f)
    {
        throw new NotImplementedException("Unable to generate a hash code for thresholds, do not use this for grouping");
    }
}

并使用它:

var result = floatList.Contains(100f, new FloatThresholdComparer(0.01f))

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