# Program to determine if 3 points lie on a line
# (user enters points)
# Matt Bishop, May  1, 2009
# for ECS 10 Spring 2009

# this routine determines if 3 points are on a line
# parameters: x1, y1: x, y co-ordinates of first point
#             x2, y2: x, y co-ordinates of second point
#             x3, y3: x, y co-ordinates of third point
# side effect: prints message giving answer
def isline(x1, y1, x2, y2, x3, y3):
    # check for everything being on horizontal line
    if (x1 == x2):
        if (x2 == x3):
            print "The points are on the same horizontal line";
        else:
            print "The points are not on the same line";
    else:
        # now compute the slope and y-intercept for 2 points
        m = (float(y2)-float(y1))/(float(x2)-float(x1));
        b = y2 - m * x2
        # now see if (x3, y3) are on the same line
        if (y3 == m * x3 + b):
            print "The points are on the same (non-horizontal) line";
        else:
            print "The points are not on the same line";

# this routine generates a prompt to ask for a point
# parameters: what: which point (first, second, third) do you want?
# returns: the prompt as a string
def prompt(what):
    # generate the prompt and return it
    s = "Enter the " + what + " point's co-ordinates separated by a comma: ";
    return s;

# now put it all together
# calls: prompt: generates user prompt
#        isline: to determine if points lie on same line
def main():
    x1, y1 = input(prompt("first"));
    x2, y2 = input(prompt("second"));
    x3, y3 = input(prompt("third"));
    isline(x1, y1, x2, y2, x3, y3);

main()