std::binary_function (3) - Linux Manuals

std::binary_function: std::binary_function

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;

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