// ENGR 131, Monday 3:30 Recitation (Amanda Rohn)
// HW #6, Part B - Dot Products

#include <iostream>
#include "useful.h"

using std::cin;
using std::cout;
using std::endl;
using aer::GetDouble;

double Dot(double a[], int a_size, double b[], int b_size);

int main()
{
	const int SIZE = 3;

	cout << "This program can calculate the dot product of two vectors (a and b) of length 3.\n";
	
	double a[SIZE], b[SIZE];

	cout << "Please enter the three elements of vector a at the prompts.\n";

	for(int i = 0; i < SIZE; i++)
		a[i] = GetDouble("Element of a");

	cout << "Now enter the elements of vector b.\n";

	for(int j = 0; j < SIZE; j++)
		b[j] = GetDouble("Element of b");

	cout << "\nThe dot product of those vectors is " << Dot(a,SIZE,b,SIZE) << endl;

	return 0;
}


double Dot(double a[], int a_size, double b[], int b_size)
{
	//if the sizes don't match, we assume that the extra elements in the smaller vector
	//are equal to zero. This is equivalent to calculating the dot product only for those
	//elements that exist in both vectors, so use the smaller size.
	int size = (a_size <= b_size) ? a_size : b_size;

	double dp = 0;

	//the dot product is found by summing the products of the matching elements in each vector
	for(int i = 0; i < size; i++)
		dp += a[i] * b[i];

	return dp;
}