std::unary_negate
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unary_negate
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Defined in header
<functional>
template< class Predicate >
struct unary_negate : public std::unary_function <Predicate::argument_type, bool>;
(until C++11)
struct unary_negate : public std::unary_function <Predicate::argument_type, bool>;
template< class Predicate >
struct unary_negate;
(since C++11) struct unary_negate;
(deprecated in C++17)
(removed in C++20)
std::unary_negate is a wrapper function object returning the complement of the unary predicate it holds.
The unary predicate type must define a member type, argument_type, that is convertible to the predicate's parameter type. The unary function objects obtained from std::ref , std::cref , std::negate , std::logical_not , std::mem_fn , std::function , std::hash , or from another call to std::not1 have this type defined, as are function objects derived from the deprecated std::unary_function .
std::unary_negate objects are easily constructed with helper function std::not1 .
Contents
[edit] Member types
Type
Definition
argument_type
Predicate::argument_type
result_type
bool
[edit] Member functions
(constructor)
(public member function)
operator()
(public member function)
std::unary_negate::unary_negate
explicit unary_negate( Predicate const& pred );
(until C++14)
constexpr explicit unary_negate( Predicate const& pred );
(since C++14)
Constructs a std::unary_negate function object with the stored predicate pred.
Parameters
pred
-
predicate function object
std::unary_negate::operator()
bool operator()( argument_type const& x ) const;
(until C++14)
constexpr bool operator()( argument_type const& x ) const;
(since C++14)
Returns the logical complement of the result of calling pred(x).
Parameters
x
-
argument to pass through to predicate
Return value
The logical complement of the result of calling pred(x).
[edit] Example
Run this code
#include <algorithm> #include <functional> #include <iostream> #include <vector> struct less_than_7 : std::unary_function <int, bool> { bool operator()(int i) const { return i < 7; } }; int main() { std::vector <int> v(7, 7); v[0] = v[1] = v[2] = 6; std::unary_negate<less_than_7> not_less_than_7((less_than_7())); // C++11 solution: // Use std::function<bool (int)> // std::function<bool (int)> not_less_than_7 = // [](int x)->bool { return !less_than_7()(x); }; std::cout << std::count_if (v.begin(), v.end(), not_less_than_7); }
Output:
4
[edit] See also
(deprecated in C++17)(removed in C++20)
(class template) [edit]
(C++23)
(class template) [edit]
(deprecated in C++17)(removed in C++20)
(function template) [edit]
(deprecated in C++11)(removed in C++17)
(function template) [edit]
(deprecated in C++11)(removed in C++17)
(class template) [edit]