binary_negate 类

一种类模板,用于提供成员函数,对指定二元函数的返回值进行求反。 在 C++17 中已弃用,以支持 not_fn

语法

template <class Operation>
class binary_negate
    : public binaryFunction <typename Operation::first_argument_type,
                              typename Operation::second_argument_type, bool>
{
    explicit binary_negate(const Operation& Func);
    bool operator()(const typename Operation::first_argument_type& left,
                    const typename Operation::second_argument_type& right) const;
};

参数

Func
要求反的二元函数。

left
要求反的二元函数的左操作数。

right
要求反的二元函数的右操作数。

返回值

二元函数的求反运算。

备注

这个类模板存储 Func 二元函数对象的副本。 它将其成员函数 operator() 定义为返回 !Func(left, right)

很少直接使用 binary_negate 的构造函数。 通常首选 Helper 函数 not2 来声明和使用 binary_negator 适配器谓词。

示例

// functional_binary_negate.cpp
// compile with: /EHsc
#define _CRT_RAND_S
#include <stdlib.h>

#include <vector>
#include <algorithm>
#include <functional>
#include <iostream>

int main( )
{
   using namespace std;
   vector <unsigned int> v1;
   vector <unsigned int>::iterator Iter1;

   unsigned int i;
   v1.push_back( 6262 );
   v1.push_back( 6262 );
   unsigned int randVal = 0;
   for ( i = 0 ; i < 5 ; i++ )
   {
      rand_s(&randVal);
      v1.push_back( randVal );
   }

   cout << "Original vector v1 = ( " ;
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
      cout << *Iter1 << " ";
   cout << ")" << endl;

   // To sort in ascending order,
   // use default binary predicate less<unsigned int>( )
   sort( v1.begin( ), v1.end( ) );
   cout << "Sorted vector v1 = ( " ;
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
      cout << *Iter1 << " ";
   cout << ")" << endl;

   // To sort in descending order,
   // use the binary_negate function
   sort( v1.begin( ), v1.end( ),
   binary_negate<less<unsigned int> >(less<unsigned int>( ) ) );

   // The helper function not2 could also have been used
   // in the above line and is usually preferred for convenience
   // sort( v1.begin( ), v1.end( ), not2(less<unsigned int>( ) ) );

   cout << "Resorted vector v1 = ( " ;
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
      cout << *Iter1 << " ";
   cout << ")" << endl;
}
Original vector v1 = ( 6262 6262 2233879413 2621500314 580942933 3715465425 3739828298 )
Sorted vector v1 = ( 6262 6262 580942933 2233879413 2621500314 3715465425 3739828298 )
Resorted vector v1 = ( 3739828298 3715465425 2621500314 2233879413 580942933 6262 6262 )