operator== <functional>

Article
12/01/2015

Tests if callable object is empty.

Syntax

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 object
npc
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