std::not1

C++

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Technical Specifications

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plus minus negate multiplies divides modulus logical_and logical_or logical_not	equal_to not_equal_to greater less greater_equal less_equal bit_and bit_or bit_xor bit_not (C++14)
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not_fn (C++17)
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Old binders and adaptors
unary_function (until C++17) binary_function (until C++17) ptr_fun (until C++17) pointer_to_unary_function (until C++17) pointer_to_binary_function (until C++17) mem_fun (until C++17) mem_fun_tmem_fun1_tconst_mem_fun_tconst_mem_fun1_t (until C++17)(until C++17)(until C++17)(until C++17) not1 (until C++20) not2 (until C++20)	binder1stbinder2nd (until C++17)(until C++17) bind1stbind2nd (until C++17)(until C++17) mem_fun_ref (until C++17) mem_fun_ref_tmem_fun1_ref_tconst_mem_fun_ref_tconst_mem_fun1_ref_t (until C++17)(until C++17)(until C++17)(until C++17) unary_negate (until C++20) binary_negate (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)

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

See also

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