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std::binary_negate

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binary_negate

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Defined in header <functional>

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

[edit] Member types

Type Definition

first_argument_type Predicate::first_argument_type

second_argument_type Predicate::second_argument_type

result_type bool

[edit] Member functions

(constructor)

constructs a new binary_negate object with the supplied predicate
(public member function)

operator()

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

pred - predicate function object

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

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).

[edit] 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

[edit] See also

binary_function

(deprecated in C++11)(removed in C++17)

adaptor-compatible binary function base class
(class template) [edit]

(C++11)

copyable wrapper of any copy constructible callable object
(class template) [edit]

move_only_function

(C++23)

move-only wrapper of any callable object that supports qualifiers in a given call signature
(class template) [edit]

(deprecated in C++17)(removed in C++20)

constructs custom std::binary_negate object
(function template) [edit]

(deprecated in C++11)(removed in C++17)

creates an adaptor-compatible function object wrapper from a pointer to function
(function template) [edit]

(deprecated in C++17)(removed in C++20)

wrapper function object returning the complement of the unary predicate it holds
(class template) [edit]

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