std::not2

性病：不是2

Defined in header
template< class Predicate > std::binary_negate<Predicate> not2(const Predicate& pred		(until C++14)
template< class Predicate > constexpr std::binary_negate<Predicate> not2(const Predicate& pred		(since C++14) (deprecated in C++17)

not2是一个助手函数，用于创建一个函数对象，该对象返回传递的二进制谓词函数的补码。创建的函数对象类型为std::binary_negate<Predicate>...

二进制谓词类型必须定义两个成员类型，first_argument_type和second_argument_type可转换为谓词%27s参数类型的。从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，，，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，或者从另一个电话到std::not2定义这些类型，就像从已弃用的函数对象派生的函数对象一样。std::binary_function...

参数

pred	-	binary predicate

返回值

std::not2返回类型为std::binary_negate<Predicate>，构造为pred...

例外

没有。

例

二次

#include <algorithm>
#include <functional>
#include <iostream>
#include <vector>
 
struct old_same : std::binary_function<int, int, bool>
{
    bool operator()(int a, int b) const { return a == b; }
};
 
struct new_same
{
    bool operator()(int a, int b) const { return a == b; }
};
 
bool same_fn(int a, int b)
{
    return a == b;
}
 
 
int main()
{
    std::vector<int> v1{0, 1, 2};
    std::vector<int> v2{2, 1, 0};
    std::vector<bool> v3(v1.size()
 
    std::cout << "negating a binary_function:\n";
    std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(),
                   std::not2(old_same())
 
    std::cout << std::boolalpha;
    for (std::size_t i = 0; i < v1.size( ++i)
        std::cout << v1[i] << ' ' << v2[i] << ' ' << v3[i] << '\n';
 
    std::cout << "negating a standard functor:\n";
    std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(),
                   std::not2(std::equal_to<int>())
 
    for (std::size_t i = 0; i < v1.size( ++i)
        std::cout << v1[i] << ' ' << v2[i] << ' ' << v3[i] << '\n';
 
    std::cout << "negating a std::function:\n";
    std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(),
                   std::not2(std::function<bool(int,int)>(new_same()))
 
    for (std::size_t i = 0; i < v1.size( ++i)
        std::cout << v1[i] << ' ' << v2[i] << ' ' << v3[i] << '\n';
 
    std::cout << "negating a std::reference_wrapper:\n";
    std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(),
                   std::not2(std::ref(same_fn))
 
    for (std::size_t i = 0; i < v1.size( ++i)
        std::cout << v1[i] << ' ' << v2[i] << ' ' << v3[i] << '\n';
 
}

二次

产出：

二次

negating a binary_function:
0 2 true
1 1 false
2 0 true
negating a standard functor:
0 2 true
1 1 false
2 0 true
negating a std::function:
0 2 true
1 1 false
2 0 true
negating a std::reference_wrapper:
0 2 true
1 1 false
2 0 true

二次

另见

not_fn (C++17)	Creates a function object that returns the complement of the result of the function object it holds (function template)
binary_negate (deprecated)	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 (deprecated)	constructs custom std::unary_negate object (function template)
ptr_fun (until C++17)	creates an adaptor-compatible function object wrapper from a pointer to function (function template)
binary_function (until C++17)	adaptor-compatible binary function base class (class template)

 © cppreference.com

在CreativeCommonsAttribution下授权-ShareAlike未移植许可v3.0。

http：//en.cppreference.com/w/cpp/实用程序/Functional/NOT 2