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std::not1

From cppreference.com
< cpp‎ | utility‎ | functional
 
 
 
Function objects


Function wrappers
(C++11)
(C++11)
Bind
(C++11)
Reference wrappers
(C++11)(C++11)
Operator wrappers
Negators
not1
Deprecated binders and adaptors
(deprecated)
(deprecated)
(deprecated)
(deprecated)
(deprecated)(deprecated)(deprecated)(deprecated)
(deprecated)
(deprecated)(deprecated)(deprecated)(deprecated)
(deprecated)(deprecated)
(deprecated)(deprecated)
 

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)

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.

Contents

[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

#include <algorithm>
#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;
    for (int i = 0; i < 10; ++i) {
        v.push_back(i);
    }
 
    std::cout << std::count_if(v.begin(), v.end(), std::not1(LessThan7())) << "\n";
 
    //same as above, but use a lambda function
    std::function<int(int)> less_than_9 = [](int x){ return x < 9; };
    std::cout << std::count_if(v.begin(), v.end(), std::not1(less_than_9)) << "\n";
}

Output:

3

[edit] See also

wrapper function object returning the complement of the unary predicate it holds
(class template) [edit]
(C++11)
wraps callable object of any type with specified function call signature
(class template) [edit]
constructs custom std::binary_negate object
(function template) [edit]
(deprecated)
creates an adaptor-compatible function object wrapper from a pointer to function
(function template) [edit]
(deprecated)
adaptor-compatible unary function base class
(class template) [edit]