<functional> operators
The latest version of this topic can be found at <functional> operators.
| operator!= | operator== |
operator==
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 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
operator!=
Tests if callable object is not 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 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 not empty.
Example
// std_tr1__functional__operator_ne.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 << "not empty == "
<< (fn0 != 0) << std::endl;
std::function<int (int)> fn1(neg);
std::cout << std::boolalpha << "not empty == "
<< (fn1 != 0) << std::endl;
return (0);
}
not empty == false
not empty == true