operator== <functional>
Tests if callable object is empty.
template<class Fty>
bool operator==(const function<Fty>& f, null_ptr_type npc);
template<class Fty>
bool operator==(null_ptr_type npc, const function<Fty>& f);
Parameters
Fty
The function type to wrap.f
The function objectnpc
A null pointer.
Remarks
The operators both take an argument that is a reference to a function object and an argument that is a null pointer constant. Both return true only if the function object is empty.
Example
// std_tr1__functional__operator_eq.cpp
// compile with: /EHsc
#include <functional>
#include <iostream>
int neg(int val)
{
return (-val);
}
int main()
{
std::function<int (int)> fn0;
std::cout << std::boolalpha << "empty == "
<< (fn0 == 0) << std::endl;
std::function<int (int)> fn1(neg);
std::cout << std::boolalpha << "empty == "
<< (fn1 == 0) << std::endl;
return (0);
}
empty == true empty == false
Requirements
Header: <functional>
Namespace: std