cmath头混乱 [英] cmath header confusion

问题描述

数学函数的命名空间是什么？全球或std？

What is the namespace for math functions? Global or std?

请考虑 cos 函数。它有3个重载。但也有来自math.h的遗产 cos 。 C不知道有关函数重载的任何内容。因此， cos（x）无法解析为 cos（float）。解决方案是显式调用单精度版本 cosf（x）。我错过了什么？

Consider cos function. It has 3 overloads. But there is also legacy cos from math.h. C doesn't know anything about function overloading. Therefore cos(x) can't be resolved to cos(float). The solution is to call the single precision version explicitly cosf(x). Did I miss anything?

谢谢。

推荐答案

通过在C ++中包括< math.c> 和< cmath> 命名空间。 I.E.包括< math.h> 也会让你重载。

You get the same functions by including <math.c> and <cmath> in C++, the only differences is the namespace. I.E. including <math.h> also gives you the overload.

理论上，使用< math.h> 为您提供在全局命名空间和std命名空间中定义的符号，同时使用< cmath> 给你在std命名空间中定义的符号，而不是在全局命名空间中。

In theory, in C++03, using <math.h> gives you the symbols defined in the global namespace and also in the std namespace while using <cmath> gives you the symbols defined in the std namespace and not in the global namespace.

实践是不同的，C ++ 0X将理论与实践对齐。 < math.h> 为您提供在全局命名空间中定义的符号，也可以在std命名空间中使用< cmath> 给你在std命名空间中定义的符号，也可能在全局命名空间中。

The practice is different and C++ 0X aligned the theory with the practice. <math.h> gives you the symbols defined in the global namespace and perhaps also in the std namespace while using <cmath> gives you the symbols defined in the std namespace and perhaps also in the global namespace.

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