negate-struct.md

description	title	ms.date	f1_keywords	helpviewer_keywords	ms.assetid
Learn more about: negate Struct	negate Struct	11/04/2016	functional/std::negate	negate struct negate class	8a372686-786e-4262-b37c-ca13dc11e62f

negate Struct

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

Syntax

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 )