std::binary_negate(3)

NAME
std::binary_negate - std::binary_negate

Synopsis
   Defined in header <functional>
   template< class Predicate >
   struct binary_negate
       : public std::binary_function<
           Predicate::first_argument_type, (until C++11)
           Predicate::second_argument_type,
           bool
       >;
   template< class Predicate > (since C++11)
   struct binary_negate; (deprecated in C++17)
                        (removed in C++20)
   std::binary_negate is a wrapper function object returning the complement of the
   binary predicate it holds.
   The binary predicate type must define two member types, first_argument_type and
   second_argument_type, that are convertible to the predicate's parameter types. The
   function objects obtained from std::owner_less, std::ref, std::cref, std::plus,
   std::minus, std::multiplies, std::divides, std::modulus, std::equal_to,
   std::not_equal_to, std::greater, std::less, std::greater_equal, std::less_equal,
   std::logical_not, std::logical_or, std::bit_and, std::bit_or, std::bit_xor,
   std::mem_fn, std::map::value_comp, std::multimap::value_comp, std::function, or from
   a call to std::not2 have these types defined, as are function objects derived from
   the deprecated std::binary_function.
   std::binary_negate objects are easily constructed with helper function std::not2.

Member types
   Type Definition
   first_argument_type Predicate::first_argument_type
   second_argument_type Predicate::second_argument_type
   result_type bool

Member functions
   constructor constructs a new binary_negate object with the supplied predicate
                 (public member function)
                 returns the logical complement of the result of a call to the stored
   operator() predicate
                 (public member function) std::binary_negate::binary_negate
   explicit binary_negate( Predicate const& pred ); (until C++14)
   constexpr explicit binary_negate( Predicate const& pred ); (since C++14)
   Constructs a std::binary_negate function object with the stored predicate pred.

Parameters
   pred - predicate function object std::binary_negate::operator()
   bool operator()( first_argument_type const& x, (until C++14)
                    second_argument_type const& y ) const;
   constexpr bool operator()( first_argument_type const& x, (since C++14)
                        second_argument_type const& y ) const;
   Returns the logical complement of the result of calling pred(x, y).

Parameters
   x - first argument to pass through to predicate
   y - second argument to pass through to predicate

Return value
   The logical complement of the result of calling pred(x, y).

Example
// Run this code
 #include <algorithm>
 #include <cstddef>
 #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;
     for (int i = 0; i < 7; ++i)
         v1.push_back(i);
     std::vector<int> v2(v1.size());
     std::reverse_copy(v1.begin(), v1.end(), v2.begin());
     std::vector<bool> v3(v1.size());
     std::binary_negate<same> not_same((same()));
     // C++11 solution:
     // std::function<bool (int, int)> not_same =
     // [](int x, int y) -> bool { return !same()(x, y); };
     std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), not_same);
     std::cout.setf(std::ios_base::boolalpha);
     for (std::size_t i = 0; i != v1.size(); ++i)
         std::cout << v1[i] << " != " << v2[i] << " : " << v3[i] << '\n';
 }

Output:
 0 != 6 : true
 1 != 5 : true
 2 != 4 : true
 3 != 3 : false
 4 != 2 : true
 5 != 1 : true
 6 != 0 : true

See also
   binary_function adaptor-compatible binary function base class
   (deprecated in C++11) (class template)
   (removed in C++17)
   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 call
   (C++23) signature
                        (class template)
   not2 constructs custom std::binary_negate object
   (deprecated in C++17) (function template)
   (removed in C++20)
   ptr_fun creates an adaptor-compatible function object wrapper from a
   (deprecated in C++11) pointer to function
   (removed in C++17) (function template)
   unary_negate wrapper function object returning the complement of the unary
   (deprecated in C++17) predicate it holds
   (removed in C++20) (class template)