std::not1 is a helper function to create a function object that returns the complement of the unary predicate function passed. The function object created is of typestd::unary_negate<Predicate>.

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.

[edit]Parameters

[edit]Return value

std::not1 returns an object of typestd::unary_negate<Predicate>, constructed withpred.

[edit]Exceptions

(none)

[edit]Example

#include <algorithm>#include <functional>#include <iostream>#include <iterator>#include <numeric>#include <vector> struct LessThan7:std::unary_function<int,bool>{bool operator()(int i)const{return i<7;}}; int main(){std::vector<int> v(10);std::iota(std::begin(v),std::end(v),0); std::cout<<std::count_if(begin(v), end(v), std::not1(LessThan7()))<<'\n'; // the same as above using std::functionstd::function<bool(int)> less_than_9=[](int x){return x<9;};std::cout<<std::count_if(begin(v), end(v), std::not1(less_than_9))<<'\n';}

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[edit]See also

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