C ++ float to int [英] C++ float to int
问题描述
也许，这是非常简单的问题，但我不能得到的答案。我已经搜索了一段时间（现在Google认为我发送自动查询 http://twitter.com/michaelsync/status / 17177278608 ）..
Maybe, it's very simple question but I couldn't get the answer. I've been searching quite a while ( now Google think that I'm sending automated queries http://twitter.com/michaelsync/status/17177278608 ) ..
int n = 4.35 *100;
cout << n;
为什么输出成为434而不是435？ 4.35 * 100 = 435这是一个整数值，这应该可以分配给整数变量n，对不对？
Why does the output become "434" instead of "435"? 4.35 * 100 = 435 which is a integer value and this should be assignable to the integer variable "n", right?
或者C ++编译器在乘法之前将4.35转换为整数吗？我认为它不会。为什么编译器自动将4.35更改为4.34，这仍然是一个float？
OR Does the C++ compiler cast 4.35 to integer before multiplying? I think it won't. Why does the compiler automatically change 4.35 to 4.34 which is still a float??
感谢。
推荐答案
这真的是只是一个起点，可悲的是，然后语言介绍自己的foibles，当他们做类型转换时，等等。在这种情况下，你只创建了一个情况，常量4.35不能精确表示，因此4.35 * 100更像434.9999999999，并且转换为 int 会 trunc ，而不是 round 。
That's really just a starting point, sadly, as then languages introduce their own foibles as to when they do type conversions, etc. In this case you've merely created a situation where the constant 4.35 can't be represented precisely, and thus 4.35*100 is more like 434.9999999999, and the cast to int does trunc, not round.
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