std::not1
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not1
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Defined in header
<functional>
template< class Predicate >
std::unary_negate <Predicate> not1( const Predicate& pred );
(until C++14)
std::unary_negate <Predicate> not1( const Predicate& pred );
template< class Predicate >
constexpr std::unary_negate <Predicate> not1( const Predicate& pred );
(since C++14) constexpr std::unary_negate <Predicate> not1( const Predicate& pred );
(deprecated in C++17)
(removed in C++20)
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 type std::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 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 .
[edit] Parameters
pred
-
unary predicate
[edit] Return value
std::not1 returns an object of type std::unary_negate <Predicate>, constructed with pred.
[edit] Exceptions
(none)
[edit] Example
Run this code
#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::function std::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'; }
Output:
3 1
[edit] See also
(C++17)
(function template) [edit]
(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]