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从cmath文件看名字是怎样被添加到命名空间std中的
2022-07-07 23:29:00 【昊虹图像算法】
std为C++中的标准命名空间,C++的标准库中的各种名字都在其中。
下面是一个使用标准命名空间std的例子。
#include <cmath>
#include <iostream>
using namespace std;
int main()
{
float x = 3.6;
int y = round(x);
cout << "y is:" << y << endl << endl;
}
运行结果如下:
在上面这个代码中,名字round、cout、endl都是std空间中的名字。
标准库math中的函数名也被添加到了std空间中,
文件cmath的百度网盘下载链接:
https://pan.baidu.com/s/1NZClfWR5ARG0WNdOOe0mZQ?pwd=wb7i
接下来我们看下cmath文件是怎么把math中的函数名字引入到std空间中的。
截图如下:
从上面的截图中我们可以看出,将名字引入std空间,
起始语句为:
_STD_BEGIN
如果我们要把名字abs引入std空间,则像下面这样写:
using _CSTD abs;
把要添加入名字写完后,按下面这样结尾:
从上面的截图中可以看出,以
_STD_END
结尾。
大概就这样。
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