| 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) |
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
| (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) | |
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,
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).
Example
#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
See also
| (until C++17) | adaptor-compatible binary function base class (class template) |
| (C++11) | wraps callable object of any type with specified function call signature (class template) |
constructs custom std::binary_negate object (function template) | |
| (until C++17) | creates an adaptor-compatible function object wrapper from a pointer to function (function template) |
| wrapper function object returning the complement of the unary predicate it holds (class template) |
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