为什么要使用！ INT转换时为bool？ [英] Why use !! when converting int to bool?

问题描述

什么可能是一个原因，这样一个整数转换成一个布尔？

What can be a reason for converting an integer to a boolean in this way?

bool booleanValue = !!integerValue;

而不仅仅是

bool booleanValue = integerValue;

我所知道的是，在VC ++ 7，后者将导致 C4800警告和前不会。有没有两者之间的任何其他区别？

All I know is that in VC++7 the latter will cause C4800 warning and the former will not. Is there any other difference between the two?

推荐答案

与!!的问题成语是它的简洁，很难看到，易误认为一个错字，容易砸！的之一，等等。我把它放在看，我们可怎么可爱与C / C ++类别。
搜索结果
只要写布尔isNonZero =（integerValue！= 0）; ...很清楚

The problems with the "!!" idiom are that it's terse, hard to see, easy to mistake for a typo, easy to drop one of the "!'s", and so forth. I put it in the "look how cute we can be with C/C++" category.

Just write bool isNonZero = (integerValue != 0); ... be clear.

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