C ++ distance function saves -1

Question

I created a program that calculates the distance between two points, and finds the slope as well.

1) How can I change the program to strictly pointers?

2) The distance function returns "-1" regardless of the input. I am 100% sure that my arithmetic is correct, but something seems to be wrong.

 // This program computes the distance between two points
 // and the slope of the line passing through these two points.

    #include<iostream>
    #include<iomanip>
    #include<cmath>
    using namespace std;

    struct Point
    {
        double x;
        double y;
    };

    double distance(Point &p1, Point &p2);
    double slope(Point &p1, Point &p2);

    int main()
    {
        Point p1, p2;
        char flag = 'y';
        cout << fixed << setprecision(2);
        while(flag == 'y' || flag == 'Y')
        {
            cout << "First x value: "; cin >> p1.x;
            cout << "First y value: "; cin >> p1.y;
            cout << "Second x value: "; cin >> p2.x;
            cout << "Second y value: "; cin >> p2.y; cout << endl;

            cout << "The distance between points (" << p1.x << ", " << p1.y << ") and (";
            cout << p2.x << ", " << p2.y << ") is " << distance(&p1, &p2);

            if ((p2.x - p1.x) == 0)
            { cout << " but there is no slope." << endl; cout << "(Line is vertical)" << endl; }
            else
            { cout << " and the slope is " << slope(p1, p2) << "." << endl; }

            cout << endl;
            cout << "Do you want to continue with another set of points?: "; cin>> flag;
            cout << endl;
        }
        return 0;
    }

    double distance(Point &p1, Point &p2)
    {
        return sqrt((pow((p2.x - p1.x), 2) + pow((p2.y - p1.y), 2)));
    }

    double slope(Point &p1, Point &p2)
    {
        return (p2.y - p1.y) / (p2.x - p1.x);
    }

Answer 1

If your code is broken:

cout << p2.x << ", " << p2.y << ") is " << distance(&p1, &p2);

You pass objects of type to a Point *function waiting Point.

Why we do not see compiler errors:

using namespace std, , , std::distance(), , &p1 &p2.

:

"namespace std" ? ?.