根据我正在阅读的书,rand()
在 C++ 中需要 #include
但是,我能够编译以下使用 rand()
的代码,而无需 #include <cstdlib>
或 using namespace std;
在 Visual 中工作室 2015.
为什么这两个不需要编译?我应该包括 cstdlib 吗?
According to the book I'm reading, rand()
requires #include <cstdlib>
in C++
However, I am able to compile the following code that uses rand()
without #include <cstdlib>
nor using namespace std;
in Visual Studio 2015.
Why are these two not needed to compile? Should I include cstdlib?
C++ 代码:
#include <iostream>
int main()
{
std::cout << rand() << std::endl;
}
有两个问题在起作用:
iostream
可以直接或间接包含 cstdlib
.cstdlib
)的头文件可以将 C 标准库名称带入全局命名空间,即在 std
命名空间之外(例如 rand
.)这是从 C++11 开始正式允许的,并且在之前被广泛容忍.iostream
may include cstdlib
directly or indirectly.cstdlib
) are allowed to bring C standard library names into the global namespace, that is, outside of the std
namespace (e.g. rand
.) This is formally allowed since C++11, and was largely tolerated before.这篇关于为什么 rand() 编译时不包含 cstdlib 或使用命名空间 std?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持跟版网!