Przeciążanie operatora dla vector

#include <iostream>
#include <vector>
#include <climits>

using namespace std;

double operator *( vector < double > v1, vector < double > v2 )
{
    int n = v1.size();
   
    for( int i = 0; i < n; i++ )
         return( v1[ i ] * v2[ i ] ) +( v1[ i + 1 ] * v2[ i + 1 ] );
   
}

int main()
{
   
    vector < double > v;
    v.reserve( 2 );
    v.push_back( 1 );
    v.push_back( 5 );
   
    vector < double > w;
    w.reserve( 2 );
    w.push_back( 2 );
    w.push_back( 5 );
   
    cout << v * w;
    cout << "\n";
   
   
    vector < double > vdwa;
    vdwa.reserve( 4 );
    vdwa.push_back( 4 );
    vdwa.push_back( 2 );
    vdwa.push_back( 4 );
    vdwa.push_back( 3 );
   
    vector < double > wdwa;
    wdwa.reserve( 4 );
    wdwa.push_back( 8 );
    wdwa.push_back( 4 );
    wdwa.push_back( 3 );
    wdwa.push_back( 6 );
   
    cout << wdwa * vdwa;
}

#include <iostream>
#include <vector>
#include <climits>

using namespace std;

double operator *( const vector < double > v1, const vector < double > v2 )
{
    int n = v1.size();
    int suma = 0;
    for( int i = 0; i < n; i++ )
         suma +=( v1[ i ] * v2[ i ] );
   
    return suma;
   
}