Computing the scalar product of two vectors in C++

Question

I am trying to write a program with a function double_product(vector a, vector b) that computes the scalar product of two vectors. T

Answer 1

You can delete the class you have defined. You don't need it.

In your scalar_product function:

double scalar_product(vector a, vector b)
{
    double product = 0;
    for (int i = 0; i <= a.size()-1; i++)
        for (int i = 0; i <= b.size()-1; i++)
            product = product + (a[i])*(b[i]);
    return product;
}

It's almost there. You don't need 2 loops. Just one.

double scalar_product(vector a, vector b)
{
    if( a.size() != b.size() ) // error check
    {
        puts( "Error a's size not equal to b's size" ) ;
        return -1 ;  // not defined
    }

    // compute
    double product = 0;
    for (int i = 0; i <= a.size()-1; i++)
       product += (a[i])*(b[i]); // += means add to product
    return product;
}

Now to call this function, you need to create 2 vector objects in your main(), fill them with values, (the same number of values of course!) and then call scalar_product( first_vector_that_you_create, second_vector_object );