C#用.Equals()比较两个double [英] C# Compare two double with .Equals()

问题描述

我使用ReShaper，当我将两个double值与==进行比较时，建议我使用数学运算.ABS方法具有公差.请参阅: https://www.jetbrains.com/help/resharper/2016.2/CompareOfFloatsByEqualityOperator.html

I use ReShaper and when I compare two double values with ==, it suggests that I should use the Math. ABS method with a tolerance. See: https://www.jetbrains.com/help/resharper/2016.2/CompareOfFloatsByEqualityOperator.html

这个例子

double d = 0.0;
double d2 = 0.0;
if (d == d2)
{
    /* some code */
}

然后转换为

double d = 0.0;
double d2 = 0.0;
if (Math.Abs(d - d2) < TOLERANCE)
{
    /* some code */
}

但是，我认为对于开发人员而言，考虑正确的容忍度确实很复杂.所以我认为可以在Double.Equals()方法中实现.

But I think it's really complicated for a developer to think about the right tolerance. So I thought this may be implemented in the Double.Equals() method.

但是这种方法是这样实现的

But this method is implemented like so

public override bool Equals(Object obj) {
    if (!(obj is Double)) { 
        return false;
    } 
    double temp = ((Double)obj).m_value; 
    // This code below is written this way for performance reasons i.e the != and == check is intentional.
    if (temp == m_value) { 
        return true;
    }
    return IsNaN(temp) && IsNaN(m_value);
}

public bool Equals(Double obj)
{ 
    if (obj == m_value) {
        return true; 
    } 
    return IsNaN(obj) && IsNaN(m_value);
}

为什么?比较双值的正确方法是什么?

推荐答案

您可以创建扩展方法

public static class DoubleExtension 
{
    public static bool AlmostEqualTo(this double value1, double value2)
    {
        return Math.Abs(value1 - value2) < 0.0000001; 
    }
}

并像这样使用它

doubleValue.AlmostEqualTo(doubleValue2)

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