nullptr_t

std::nullptr_t^[1]是c++空指针类型的文字，nullptr.在c++11中引入的

如果两个或两个以上的重载接受不同的指针类型，过载std::nullptr_t是需要接受一个空指针参数.

#include

#include

voidf(int*pi)

{

std::cout<<"Pointertointegeroverload\n";

}

voidf(double*pd)

{

std::cout<<"Pointertodoubleoverload\n";

}

voidf(std::nullptr_tnullp)

{

std::cout<<"nullpointeroverload\n";

}

intmain(){

int*pi;double*pd;

f(pi);

f(pd);

f(nullptr);//wouldbeambiguouswithoutvoidf(nullptr_t)//f(NULL);//ambiguousoverload:allthreefunctionsarecandidates

}

Pointertointegeroverload

Pointertodoubleoverload

nullpointeroverload