std::binary_negate (3) - Linux Manuals

std::binary_negate: std::binary_negate

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)

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.
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

              constructs a new binary_negate object with the supplied predicate
constructor (public member function)
              returns the logical complement of the result of a call to the stored predicate
operator() (public member function)

 std::binary_negate::binary_negate

explicit binary_negate( Predicate const& pred ); (until C++14)
explicit constexpr binary_negate( Predicate const& pred ); (since C++14)

Constructs a 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 <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;
      std::vector<int> v2;
      for (int i = 0; i < 10; ++i) v1.push_back(i);
      for (int i = 0; i < 10; ++i) v2.push_back(10 - i);

      std::vector<bool> v3(v1.size());

      std::binary_negate<same> not_same((same()));

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

      /* C++11 solution:
          // Use std::function<bool (int, int)>
          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 (int i = 0; i < 10; ++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