std::binary_negate - cppreference.com (original) (raw)

| Defined in header | | | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | ------------------------------------------------------ | | template< class Predicate > struct binary_negate : public std::binary_function< Predicate::first_argument_type, Predicate::second_argument_type, bool >; | | (until C++11) | | template< class Predicate > struct binary_negate; | | (since C++11) (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.

Contents

• 1 Member types
• 2 Member functions
• 3 std::binary_negate::binary_negate
  • 3.1 Parameters
• 4 std::binary_negate::operator()
  • 4.1 Parameters
  • 4.2 Return value
  • 4.3 Example
  • 4.4 See also

[edit] Member types

[edit] Member functions

| | 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 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

std::binary_negate::operator()

| bool operator()( first_argument_type const& x, second_argument_type const& y ) const; | | (until C++14) | | --------------------------------------------------------------------------------------------------- | | ------------- | | constexpr bool operator()( first_argument_type const& x, second_argument_type const& y ) const; | | (since C++14) |

Returns the logical complement of the result of calling pred(x, y).

Parameters

Return value

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

[edit] Example

#include #include #include #include #include   struct same : std::binary_function<int, int, bool> { bool operator()(int a, int b) const { return a == b; } };   int main() { std::vector v1; for (int i = 0; i < 7; ++i) v1.push_back(i);   std::vector v2(v1.size()); std::reverse_copy(v1.begin(), v1.end(), v2.begin());   std::vector v3(v1.size());   std::binary_negate 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

[edit] See also