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std::unary_negate(3) C++ Standard Libary std::unary_negate(3) NAME std::unary_negate - std::unary_negate Synopsis Defined in header <functional> template< class Predicate > struct unary_negate : public (until C++11) std::unary_function<Predicate::argument_type, bool>; (since C++11) template< class Predicate > (deprecated in struct unary_negate; C++17) (re- moved in C++20) 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. unary_negate objects are easily constructed with helper function std::not1. Member types Type Definition argument_type Predicate::argument_type result_type bool Member functions constructor constructs a new unary_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::unary_negate::unary_negate explicit unary_negate( Predicate const& pred ); (until C++14) explicit constexpr unary_negate( Predicate const& pred ); (since C++14) Constructs a 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). 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; for (int i = 0; i < 10; ++i) v.push_back(i); std::unary_negate<less_than_7> not_less_than_7((less_than_7())); std::cout << std::count_if(v.begin(), v.end(), not_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: 3 See also binary_negate wrapper function object returning the comple- ment of the binary (deprecated in C++17) predicate it holds (removed in C++20) (class template) function wraps callable object of any copy con- structible type with (C++11) specified function call signature (class template) move_only_function wraps callable object of any type with speci- fied function call (C++23) signature (class template) not1 constructs custom std::unary_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_function adaptor-compatible unary function base class (deprecated in C++11) (class template) (removed in C++17) http://cppreference.com 2022.07.31 std::unary_negate(3)
NAME | Synopsis | Member types | Member functions | Parameters | Parameters | Return value | Example | Output: | See also
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