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std::not2

From cppreference.com
 
 
 
Function objects
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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. The function objects obtained from std::owner_less, std::ref, std::cref, std::plus, std::minus, std::multiplies, std::divides, std::modulus, std::equal_to, std::not_equal_to, std::greater, {{c|std::less}], std::greater_equal, std::less_equal, std::logical_not, std::logical_or, std::bit_and, std::bit_or, std::bit_xor, std::mem_fn, std::map::value_comp, std::multimap::value_comp, std::function, or from another call to std::not2 have these types defined, as are function objects derived from the deprecated std::binary_function.

Contents

[edit] Parameters

pred - unary predicate

[edit] Return value

std::not2 returns an object of type std::binary_negate<Predicate>, constructed with pred.

[edit] Exceptions

None.

[edit] Example

#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

wrapper function object returning the complement of the binary 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::unary_negate object
(function template) [edit]
(deprecated)
creates an adaptor-compatible function object wrapper from a pointer to function
(function template) [edit]
(deprecated)
adaptor-compatible binary function base class
(class template) [edit]