plus Struct

A predefined function object that performs the addition operation (binary operator+) on its arguments.

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

// specialized transparent functor for operator+
template<> struct plus<void>
   {
   template<class Type1, class Type2>
      auto operator()(Type1&& Left, Type2&& Right) const
      -> decltype(std::forward<Type1>(Left)
         + std::forward<Type2>(Right));
   };

Type, Type1, Type2

A type that supports a binary operator+ that takes operands of the specified or inferred types.

Left

The left operand of the addition operation. The unspecialized template takes an lvalue reference argument of type Type. The specialized template does perfect forwarding of lvalue and rvalue reference arguments of inferred type Type1.

Right

The right operand of the addition operation. The unspecialized template takes an lvalue reference argument of type Type. The specialized template does perfect forwarding of lvalue and rvalue reference arguments of inferred type Type2.

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

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

using namespace std;

int main( )
{
   vector <double> v1, v2, v3 ( 6 );
   vector <double>::iterator Iter1, Iter2, Iter3;
   
   int i;
   for ( i = 0 ; i <= 5 ; i++ )
      v1.push_back( 4 * i );

   int j;
   for ( j = 0 ; j <= 5 ; j++ )
      v2.push_back( -2.0 * j - 4 );

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

   cout << "The vector v2 = ( " ;
   for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
      cout << *Iter2 << " ";
   cout << ")" << endl;

   // Finding the element-wise sums of the elements of v1 & v2
   transform (v1.begin( ), v1.end( ), v2.begin( ), v3.begin ( ), plus<double>( ) );

   cout << "The element-wise sums are: ( " ;
   for ( Iter3 = v3.begin( ) ; Iter3 != v3.end( ) ; Iter3++ )
      cout << *Iter3 << " ";
   cout << ")" << endl;
}
The vector v1 = ( 0 4 8 12 16 20 )
The vector v2 = ( -4 -6 -8 -10 -12 -14 )
The element-wise sums are: ( -4 -2 0 2 4 6 )

Header: <functional>

Namespace: std

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