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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);


The function type to wrap.


The function object


A null pointer.

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.


// 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

Header: <functional>

Namespace: std

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