浮点数用C比较 [英] Comparing floating point numbers in C

问题描述

我有一个双击的打印为 0.000000 和我试图把它比 0.0 ，未果。为什么会有这个区别就在这里？什么是最可靠的方法来确定你的双零？

I've got a double that prints as 0.000000 and I'm trying to compare it to 0.0f, unsuccessfully. Why is there a difference here? What's the most reliable way to determine if your double is zero?

推荐答案

要确定是否足以零接近，它将为 0.000000 打印6位小数，东西这样的：

To determine whether it's close enough to zero that it will print as 0.000000 to six decimal places, something like:

fabs(d) < 0.0000005

小误差在处理浮点运算可以得到一般比较复杂，虽然。

Dealing with small inaccuracies in floating-point calculations can get quite complicated in general, though.

如果你想有一个更好的想法是什么珍惜你所拥有，尝试用％G 打印，而不是％F 。

If you want a better idea what value you've got, try printing with %g instead of %f.

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