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binary_negate Class

A template class providing a member function that negates the return value of a specified binary function.

template<class Operation> 
   class binary_negate 
      : public binary_function < 
         typename Operation::first_argument_type, 
         typename Operation::second_argument_type,  
         bool>  
   { 
   public: 
   explicit binary_negate( 
      const Operation& _Func 
   ); 
   bool operator()( 
      const typename Operation::first_argument_type& _Left, 
      const typename Operation::second_argument_type& _Right 
   ) const; 
   };

_Func

The binary function to be negated.

_Left

The left operand of the binary function to be negated.

_Right

The right operand of the binary function to be negated.

The negation of the binary function.

The template class stores a copy of a binary function object _Func. It defines its member function operator() as returning !_Func(_Left, _Right).

The constructor of binary_negate is rarely used directly. The helper function not2 is usually preferred to declare and use the binary_negator adaptor predicate.

// 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 )

Header: <functional>

Namespace: std

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