# 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):
    try:
        # 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";
    except ZeroDivisionError:
        # only way to get here is if you divide by 0
        if (x2 == x3):
            print "The points are on the same 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
#        peri: to compute perimeter
def main():
    try:
        x1, y1 = input(prompt("first"));
        x2, y2 = input(prompt("second"));
        x3, y3 = input(prompt("third"));
    except NameError:
        print"\nYou didn't enter two numbers"
    except TypeError:
        print "\nAt least one of your inputs was not a number"
    except SyntaxError:
        print "\nYour input was malformed (needs a comma)"
    # this is very bad style; it's for demonstration only!
    except:
        print "\nI don't know what went wrong, but something did!"
    isline(x1, y1, x2, y2, x3, y3);


main()