为什么这个问题的结果是不同的？ [英] Why the result is different for this problem?

问题描述

我遇到了这个算术问题。

但是结果与正常的数学运算不同，为什么会这样？

  double d1 = 1.000001; 
 
 double d2 = 0.000001; 
 
 Console.WriteLine（（d1-d2）== 1.0）; 
  

解决方案

我猜你在Jon Skeet的Brainteasers页面？答案在同一网站上列出并解释此处。

作为参考，这里是从该页复制的答案。

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< 3）傻算法

计算机的本意是算术，不是吗？为什么打印出False？

  double d1 = 1.000001;双d2 = 
 0.000001; Console.WriteLine（（D1-D2）== 1.0）; 
  

答案：这里的所有值都以二进制浮点形式存储。虽然1.0可以精确地存储，1.000001实际上存储为
1.0000009999999999177333620536956004798412322998046875，而0.000001实际上存储为
0.000000999999999999999954748111825886258685613938723690807819366455078125。它们之间的差异不完全是1.0，实际上差别也不能完全保存。

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I came across this following arithmetic problem.

But the result is different from normal maths operation, Why is it so?

double d1 = 1.000001;

double d2 = 0.000001;

Console.WriteLine((d1-d2)==1.0);

解决方案

I presume you found the question on Jon Skeet's Brainteasers page? The answers are listed and explained here on the same website.

For a matter of reference, here's the answer copied from that page.

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3) Silly arithmetic

Computers are meant to be good at arithmetic, aren't they? Why does this print "False"?

double d1 = 1.000001; double d2 =
0.000001; Console.WriteLine((d1-d2)==1.0);

Answer: All the values here are stored as binary floating point. While 1.0 can be stored exactly, 1.000001 is actually stored as 1.0000009999999999177333620536956004798412322998046875, and 0.000001 is actually stored as 0.000000999999999999999954748111825886258685613938723690807819366455078125. The difference between them isn't exactly 1.0, and in fact the difference can't be stored exactly either.

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