Std::not1 (3) Linux Manual Page

std::not1 – std::not1

Synopsis

Defined in header <functional>
template< class Predicate > (until C++14)
std::unary_negate<Predicate> not1(const Predicate& pred);
template< class Predicate > (since C++14)
constexpr std::unary_negate<Predicate> not1(const Predicate& pred); (deprecated in C++17)
(removed in C++20)
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.

Parameters

pred – unary predicate

Return value

std::not1 returns an object of type std::unary_negate<Predicate>, constructed with pred.

Exceptions

None.

Example

// Run this code

#include <algorithm>

#include <numeric>

#include <iterator>

#include <functional>

#include <iostream>

#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(begin(v), end(v), 0);
    std::cout << std::count_if(begin(v), end(v), std::not1(LessThan7())) << "\n";
    // same as above, but 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

not_fn Creates a function object that returns the complement of the result of the function object it holds
                      (function template)
(C++17)
unary_negate wrapper function object returning the complement of the unary predicate it holds
                      (class template)
(deprecated in C++17)
(removed in C++20)
function wraps callable object of any type with specified function call signature
                      (class template)
(C++11)
not2 constructs custom std::binary_negate object
                      (function template)
(deprecated in C++17)
(removed in C++20)
ptr_fun creates an adaptor-compatible function object wrapper from a pointer to function
                      (function template)
(deprecated in C++11)
(removed in C++17)
unary_function adaptor-compatible unary function base class
                      (class template)
(deprecated in C++11)
(removed in C++17)

std::not1 (3) Linux Manual Page