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std::not1

From cppreference.com
< cpp‎ | utility‎ | functional
 
 
Utilities library
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Function objects
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(until C++17*)(until C++17*)(until C++17*)(until C++17*)
not1
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(until C++17*)
(until C++17*)(until C++17*)(until C++17*)(until C++17*)
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(until C++20*)
 
Defined in header <functional>
template< class Predicate >
std::unary_negate <Predicate> not1( const Predicate& pred );
(until C++14)
template< class Predicate >
constexpr std::unary_negate <Predicate> not1( const Predicate& pred );
(since C++14)
(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)
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 unary predicate it holds
(class template) [edit]
(C++11)
copyable wrapper of any copy constructible callable object
(class template) [edit]
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 custom std::binary_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]
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