std::binary_function(3)

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

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)