std::binary_function (3) Linux Manual Page

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;

binary_function is a base class for creating function objects with two arguments.
binary_function does not define operator(); it is expected that derived classes will define this. 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 binary_function is an easy way to make them compatible with those adaptors.
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<int> v1{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    std::vector<int> v2{10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0};
    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:

  0 10 true
  1 9 true
  2 8 true
  3 7 true
  4 6 true
  5 5 false
  6 4 true
  7 3 true
  8 2 true
  9 1 true
  10 0 true

See also

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