NAME¶

std::binary_function - std::binary_function

Synopsis¶

Defined in header <functional>
template<

class Arg1, (deprecated in C++11)
class Arg2, (removed in C++17)
class Result

> struct binary_function;

std::binary_function is a base class for creating function objects with two
arguments.

std::binary_function does not define operator(); it is expected that derived classes
will define this. std::binary_function provides only three types -
first_argument_type, second_argument_type and result_type - defined by the template
parameters.

Some standard library function object adaptors, such as std::not2, require the
function objects they adapt to have certain types defined; std::not2 requires the
function object being adapted to have two types named first_argument_type and
second_argument_type. Deriving function objects that take two arguments from
std::binary_function is an easy way to make them compatible with those adaptors.

std::binary_function is deprecated in C++11 and removed in C++17.

Member types¶

Type Definition
first_argument_type Arg1
second_argument_type Arg2
result_type Result

Example¶

// Run this code

#include <algorithm>
#include <functional>
#include <iostream>
#include <vector>

struct same : std::binary_function<int, int, bool>
{
bool operator()(int a, int b) const { return a == b; }
};

int main()
{
std::vector<char> v1{'A', 'B', 'C', 'D', 'E'};
std::vector<char> v2{'E', 'D', 'C', 'B', 'A'};
std::vector<bool> v3(v1.size());

std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(same()));

std::cout << std::boolalpha;
for (std::size_t i = 0; i < v1.size(); ++i)
std::cout << v1[i] << " != " << v2[i] << " : " << v3[i] << '\n';
}

Output:¶

A != E : true
B != D : true
C != C : false
D != B : true
E != A : true

See also¶

function wraps callable object of any copy constructible type with
(C++11) specified function call signature
(class template)
move_only_function wraps callable object of any type with specified function
(C++23) call signature
(class template)
ptr_fun creates an adaptor-compatible function object wrapper
(deprecated in C++11) from a pointer to function
(removed in C++17) (function template)
pointer_to_binary_function adaptor-compatible wrapper for a pointer to binary
(deprecated in C++11) function
(removed in C++17) (class template)
unary_function adaptor-compatible unary function base class
(deprecated in C++11) (class template)
(removed in C++17)