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)