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Defined in header <functional> | ||
template<class Predicate> std::binary_negate<Predicate> not2(const Predicate& pred); | (until C++14) | |
template<class Predicate> constexprstd::binary_negate<Predicate> not2(const Predicate& pred); | (since C++14) (deprecated in C++17) (removed in C++20) | |
std::not2 is a helper function to create a function object that returns the complement of the binary predicate function passed. The function object created is of typestd::binary_negate<Predicate>.
The binary predicate type must define two member types,first_argument_type andsecond_argument_type, that are convertible to the predicate's parameter types. The function objects obtained fromstd::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 another call tostd::not2 have these types defined, as are function objects derived from the deprecatedstd::binary_function.
Contents |
| pred | - | binary predicate |
std::not2 returns an object of typestd::binary_negate<Predicate>, constructed withpred.
(none)
#include <algorithm>#include <cstddef>#include <functional>#include <iostream>#include <vector> struct old_same:std::binary_function<int,int,bool>{bool operator()(int a,int b)const{return a== b;}}; struct new_same{bool operator()(int a,int b)const{return a== b;}}; bool same_fn(int a,int b){return a== b;} int main(){std::vector<int> v1{0,1,2};std::vector<int> v2{2,1,0};std::vector<bool> v3(v1.size()); std::cout<<"negating a binary_function:\n";std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(old_same())); std::cout<<std::boolalpha;for(std::size_t i=0; i< v1.size();++i)std::cout<< v1[i]<<' '<< v2[i]<<' '<< v3[i]<<'\n'; std::cout<<"negating a standard functor:\n";std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(std::equal_to<int>())); for(std::size_t i=0; i< v1.size();++i)std::cout<< v1[i]<<' '<< v2[i]<<' '<< v3[i]<<'\n'; std::cout<<"negating a std::function:\n";std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(std::function<bool(int,int)>(new_same()))); for(std::size_t i=0; i< v1.size();++i)std::cout<< v1[i]<<' '<< v2[i]<<' '<< v3[i]<<'\n'; std::cout<<"negating a std::reference_wrapper:\n";std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(std::ref(same_fn))); for(std::size_t i=0; i< v1.size();++i)std::cout<< v1[i]<<' '<< v2[i]<<' '<< v3[i]<<'\n';}
Output:
negating a binary_function:0 2 true1 1 false2 0 truenegating a standard functor:0 2 true1 1 false2 0 truenegating a std::function:0 2 true1 1 false2 0 truenegating a std::reference_wrapper:0 2 true1 1 false2 0 true
(C++17) | creates a function object that returns the complement of the result of the function object it holds (function template)[edit] |
(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 binary function base class (class template)[edit] |
