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Defined in header <functional> | ||
template<class Predicate> struct unary_negate:publicstd::unary_function<Predicate::argument_type,bool>; | (until C++11) | |
template<class Predicate> struct unary_negate; | (since C++11) (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 fromstd::ref,std::cref,std::negate,std::logical_not,std::mem_fn,std::function,std::hash, or from another call tostd::not1 have this type defined, as are function objects derived from the deprecatedstd::unary_function.
std::unary_negate objects are easily constructed with helper functionstd::not1.
Contents |
| Type | Definition |
argument_type | Predicate::argument_type |
result_type | bool |
(constructor) | constructs a new unary_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) |
explicit unary_negate( Predicateconst& pred); | (until C++14) | |
constexprexplicit unary_negate( Predicateconst& pred); | (since C++14) | |
Constructs astd::unary_negate function object with the stored predicatepred.
| pred | - | predicate function object |
bool operator()( argument_typeconst& x)const; | (until C++14) | |
constexprbool operator()( argument_typeconst& x)const; | (since C++14) | |
Returns the logical complement of the result of callingpred(x).
| x | - | argument to pass through to predicate |
The logical complement of the result of callingpred(x).
#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
(deprecated in C++17)(removed in C++20) | wrapper function object returning the complement of the binary predicate it holds (class template)[edit] |
(C++11) | copyable wrapper of any copy constructible callable object (class template)[edit] |
(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 customstd::unary_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++11)(removed in C++17) | adaptor-compatible unary function base class (class template)[edit] |
