#include <iostream>
#include <vector>

using namespace std;

//A version of the dot product function using vector class
double dot(vector<double> x, vector<double> y)
{
 //Initialise the answer
 double answer = 0.0;

 //If the vectors are not of the same size, die
 if(x.size() != y.size())
  {
   cout << "Vector argments to dot(x,y) are not the same size" << endl;
   exit(1);
  }
//Otherwise
 else
  {
   //Loop over each entry of the vector and add the product to the result
   for(unsigned int i=0;i<x.size();i++)
    {
     answer += x[i]*y[i];
    }
  }

 //Return the answer
 return answer;
}

//Main code
int main()
{
 //Declare a couple of vectors of dimension 3
 vector<double> x(3), y(3);

 x[0] = 1.0; x[1] =  2.0;  x[2] = 3.0;
 y[0] = 5.0; y[1] = -1.0; y[2] = 10.0;

 //Print out the dot product, the answer should be 5 - 2 + 30 = 33
 cout << dot(x,y) << endl;

}