On 04/10/10 16:24, Mark Tolonen wrote: > > "Chris Rebert" <c...@rebertia.com> wrote in message > news:y2o50697b2c1004091304u627d99bfj44ad56fa76a3c...@mail.gmail.com... >> On Fri, Apr 9, 2010 at 11:43 AM, John Nagle <na...@animats.com> wrote: >>> Chris Rebert wrote: >>>> On Fri, Apr 9, 2010 at 8:04 AM, Peyman Askari >>>> <peter_peyman_...@yahoo.ca> >>>> wrote: >>>>> >>>>> Hello >>>>> >>>>> This is partly Python related, although it might end up being more >>>>> math >>>>> related. >>>>> >>>>> I am using PyGTK (GUI builder for Python) and I need to find the >>>>> intersection point for two lines. It is easy to do, even if you >>>>> only have >>>>> the four points describing line segments >>>>> (http://www.maths.abdn.ac.uk/~igc/tch/eg1006/notes/node23.html). >>>>> However, it >>>>> requires that you solve for two equations. How can I do this in >>>>> Python, >>>>> either solve equations, or calculating intersection points some >>>>> other way? >>>> >>>> Just solve the equations ahead of time by using generic ones. >> <snip> >>>> x = (c - b) / (m-n) >>> >>> Actually, you don't want to do it that way, because it fails for >>> vertical >>> lines, when m and n go to infinity. >> >> As the programmer said upon seeing a stripe-less zebra: >> "Oh no, a special case!" >> >> Excellent catch my good sir; although I will point out that strictly >> speaking, you can't put vertical lines into slope-intercept form (but >> I should not have forgotten that precondition). > > And parallel lines, where m and n are equal (divide-by-zero)...
This is actually one place where non-stop arithmetic can be a good thing. With non-stop arithmetic, when you divide by zero, you get infinity and everything turns out quite well. -- http://mail.python.org/mailman/listinfo/python-list
