Question on if, while, for

[Hans Kristian Ruud]

Paul Rubin wrote:

> c at tech.usd253.org (Fred) writes:
> > I have written a simple program that I want to simplify. I used if and
> > elif. But I am sure this can be simplified with for or while. Or what
> > if I wrote a function to do the testing?
> >
> > Please DO NOT re-write this for me I want to figure it out for myself.
> > I would just like to know what is the BEST way to do it:
> >
> > 1) For loop (nested??)
> > 2) While loop
> > 3) Function
> > 4) Leave it alone it's fine??
>
> 5) Try to take a clearer look at the problem you're solving, rather
> than getting wrapped up in the programming details.  You're trying to
> reduce a fraction to lowest terms.  Never mind programming--how would
> you explain that process to a math student?  I don't think you'd do it
> the same way your program does it.  Try to make your program more
> closely follow the methods you'd learn in a math class for reducing
> fractions.  Only after you understand the math should you try to
> express it as Python code.
>
> I'll give a hint: you'll want to know how to compute the least common
> denominator of two integers a and b.  You might want to look in a book
> to find out how to do that.

And to spoil all the fun, here is a solution

>>> def gcd(a, b):
...  while a > 0:
...   print 'a = %d, b = %d' % (a, b)
...   rest = b % a
...   b = a
...   a = rest
...  return b
...
>>> gcd(4, 6)
a = 4, b = 6
a = 2, b = 4
2

- hans kristian -