C#乘法错误(双精度)[从C#论坛转发] [英] C# Multiplication error (double) [ Repost from C# forum ]

问题描述

当我做一些简单的事情时，例如

When I do some thing simple like

double result = 3.1*4.1;

结果是12.709999999999999

我本来希望12.710000000000000

the result is 12.709999999999999

I would have expected 12.710000000000000


Is this normal for C#?

推荐答案

这是正常的，浮点数不能始终表示值的准确表示.如果要显示四舍五入的数字，则ToString()方法提供了该功能.

This is normal, floating point numbers cannot always depict an accurate representation of a value. If you want to display the number rounded then the ToString() method offers that capability.

有一个经典文本，

There is a classic text, What Every Computer Scientist Should Know About Floating-Point Arithmetic[^] by David Goldberg that should help you understand what''s happening here. It''s not specific to C#, but rather the IEEE 754 standard for floating-point numbers that C# uses.

Suffice to say, it is normal, merely a common rounding error, similar to what you might have encountered in grade school when trying to represent the result of an expression such as 10 / 3 in decimal form...

我遇到了同样的问题.我发现的唯一解决方案是将值转换为小数，然后将它们相乘，然后转换为Double.那是昂贵的，但是如果没有其他解决方案可用，那就可以接受.

I had the same problem. The only solution I found is to convert the values to decimals, multiply them and after that convert to Double. That''s expensive, but if no other solution is available, is acceptable.

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