/** Return the distance between two points

    This function returns the distance between two points
    according to the Euclidean distance formula.

    @param x0 The x-coordinate of the first point
    @param y0 The y-coordinate of the first point
    @param x1 The x-coordinate of the second point
    @param y1 The y-coordinate of the second point
    @return The distance between the two points
*/
double
distance(double x0, double y0, double x1, double y1);
