std::not2

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Defined in header `<functional>`

template< class Predicate > std::binary_negate<Predicate> not2(const Predicate& pred);

not2 is a helper function to create a function object that returns the complement of the binary predicate function passed. The function object created is of type std::binary_negate<Predicate>.

The binary predicate type must define two member types, first_argument_type and second_argument_type, that are convertible to the predicate's parameter types. Binary function objects derived from std::binary_function will have this type defined, as will functions wrapped in a call to std::ptr_fun. In C++11, a std::function specialization for binary functions provides this type.

#include <algorithm>
#include <functional>
#include <iostream>
#include <vector>
 
struct same : std::binary_function<int, int, bool>
{
    bool operator()(int a, int b) const { return a == b; }
};
 
int main()
{
    std::vector<int> v1;
    std::vector<int> v2;
    for (int i = 0; i < 10; ++i) v1.push_back(i);
    for (int i = 0; i < 10; ++i) v2.push_back(10 - i);
 
    std::vector<bool> v3(v1.size());
 
    std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(same()));
 
    /* C++11 solution:
        // Use std::function<bool (int, int)> to create or wrap the predicate type
        std::function<bool (int, int)> same = [](int x, int y){ return x == y; };
 
        std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(same));
    */
 
    std::cout.setf(std::ios_base::boolalpha);
    for (int i = 0; i < 10; ++i)
        std::cout << v1[i] << ' ' << v2[i] << ' ' << v3[i] << '\n';
}

Output:

0 10 true
1 9 true
2 8 true
3 7 true
4 6 true
5 5 false
6 4 true
7 3 true
8 2 true
9 1 true

[edit] See also


binary_negate	wrapper function object returning the complement of the binary predicate it holds (class template)

function (C++11)	wraps callable object of any type with specified function call signature (class template)

not1	constructs custom std::unary_negate object (function template)

ptr_fun (deprecated)	creates an adaptor-compatible function object wrapper from a pointer to function (function template)

binary_function (deprecated)	adaptor-compatible binary function base class (class template)

std::not2

From Cppreference

Contents

[edit] Parameters

[edit] Return value

[edit] Exceptions

[edit] Example

[edit] See also