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negate Struct

A predefined function object that performs the arithmetic negation operation (unary operator-) on its argument.

template<class Type = void>
   struct negate : public unary_function<Type, Type> 
   {
      Type operator()(
         const Type& Left
      ) const;
   };

// specialized transparent functor for unary operator-
template<>
   struct negate<void>
   {
      template<class Type>
      auto operator()(Type&& Left) const
         -> decltype(-std::forward<Type>(Left));
   };

Parameters

  • Type
    Any type that supports an operator- that takes an operand of the specified or inferred type.

  • Left
    The operand to be negated. The specialized template does perfect forwarding of lvalue and rvalue reference arguments of inferred type Type.

Return Value

The result of -Left. The specialized template does perfect forwarding of the result, which has the type that's returned by unary operator-.

Example

// functional_negate.cpp
// compile with: /EHsc
#include <vector>
#include <functional>
#include <algorithm>
#include <iostream>

using namespace std;

int main( )
{
   vector <int> v1, v2 ( 8 );
   vector <int>::iterator Iter1, Iter2;
   
   int i;
   for ( i = -2 ; i <= 5 ; i++ )
   {
      v1.push_back( 5 * i );
   }

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

   // Finding the element-wise negatives of the vector v1
   transform ( v1.begin( ),  v1.end( ), v2.begin( ), negate<int>( ) );

   cout << "The negated elements of the vector = ( " ;
   for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
      cout << *Iter2 << " ";
   cout << ")" << endl;
}
The vector v1 = ( -10 -5 0 5 10 15 20 25 )
The negated elements of the vector = ( 10 5 0 -5 -10 -15 -20 -25 )

Requirements

Header: <functional>

Namespace: std

See Also

Reference

Thread Safety in the C++ Standard Library

Standard Template Library