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.
std::not1 returns an object of type std::unary_negate<Predicate>, constructed with pred.
(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::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:
[edit] See also creates a function object that returns the complement of the result of the function object it holds(deprecated in C++17)(removed in C++20)
wrapper function object returning the complement of the unary predicate it holds(deprecated in C++17)(removed in C++20)
constructs custom std::binary_negate object(deprecated in C++11)(removed in C++17)
creates an adaptor-compatible function object wrapper from a pointer to function(deprecated in C++11)(removed in C++17)
adaptor-compatible unary function base classRetroSearch is an open source project built by @garambo | Open a GitHub Issue
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