将头文件中的特定函数包含在c ++中的代码中 [英] Include specific function from a header file into the code in c++

问题描述

在python中，可以从不同的模块导入特定的功能集，而不是导入整个文件

In python, one can import specific feature-sets from different modules, rather than importing the whole file

ex：

而不是使用导入数学并使用 print math.sqrt（4），导入该函数直接：

Instead of using import math and using print math.sqrt(4), importing the function directly:

from math import sqrt
print sqrt(4)

它运作正常。

And it works just fine.

在 C 和 C ++ 中，必须包含整个头文件才能够只使用它提供的一个功能。例如，在C ++中

Where as in C and C++, one has to include the whole header file to be able to use just one function that it provides. Such as, in C++

#include<iostream>
#include<cmath>
int main(){
    cout<<sqrt(4);
    return 0;
}

C 代码将也是类似的（不一样）。

C code will also be similar (not same).

是否有可能就像在python的情况下一样，可以只包含头文件中的一个函数到他们的程序中？

ex：包括 cmath中的 sqrt（）函数/ code>？


可以吗？

Is it possible that just like as it was in case of python, one can include just one function from a header file into their program?
ex: including just the sqrt() function from cmath?

Could it be done?

推荐答案

不，这是不可能的。 C ++缺少一个真正的模块系统，所以我们留下了预处理器包含。添加新类型模块系统的提议没有进入C ++ 11。请参阅 C ++模块 - 为什么要从C ++ 0x中删除它们？他们会在稍后回来吗？以获取有关该提案的更多信息。

No, it is not possible. C++ lacks a true module system, so we are left with preprocessor includes. A proposal to add a new kind of module system did not make it into C++11. See C++ Modules - why were they removed from C++0x? Will they be back later on? for more information on that proposal.

如果这是关于您自己的库，您唯一的机会是将库分成较小的独立图书馆。如果图书馆不是你的和/或你不能改变它，你将不得不忍受它。但无论如何，真正的问题是什么？

If this is about your own library, your only chance is to split the library into smaller, independent libraries. If the library is not yours and/or you cannot change it, you'll have to live with it. But what's the real problem, anyway?

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