过载与c标准中的默认参数

我正在阅读另一个问题,它让我想起了.标准通常指定在其描述中具有默认参数的函数.标准是否允许将这些写入重载代替？

例如,标准说std :: basic_string :: copy有以下声明：

size_type copy(Ch* p,size_type n,size_type pos = 0) const;

标准库的一致性实现可以实现这两个这样的功能吗？

size_type copy(Ch* p,size_type pos) const;
size_type copy(Ch* p,size_type n) const;

在这个例子中,第二个版本可以跳过if(pos> size()){throw out_of_range(); }测试是第一个必要的.一个微优化,但是你仍然看到了这个例子.

解决方法

Could a conforming implementation of the standard library implement this instead as two functions like this?

是. C标准(C 03 17.4.4.4/2-3)说：

An implementation can declare additional non-virtual member function signatures within a [Standard Library] class:

— by adding arguments with default values to a member function signature; the same latitude does not extend to the implementation of virtual or global or non-member functions,however.

— by replacing a member function signature with default values by two or more member function signatures with equivalent behavior;

— by adding a member function signature for a member function name.

A call to a member function signature described in the C + + Standard library behaves the same as if the implementation declares no additional member function signatures

原文地址：https://www.jb51.cc/c/113441.html