On Oct 30, 10:25 am, "J. Clifford Dyer" <[EMAIL PROTECTED]> wrote: > On Tue, Oct 30, 2007 at 01:09:38PM +0100, Boris Borcic wrote regarding Re: > Iteration for Factorials: > > > > > Py-Fun wrote: > > > I'm stuck trying to write a function that generates a factorial of a > > > number using iteration and not recursion. Any simple ideas would be > > > appreciated. > > > fact = lambda n : len(map([1].__imul__,range(1,n+1))[0]) > > OK. Now I've been sucked in. How about this: > > def fact(x): > def f(x): > if int(x) != x: > raise ValueError > elif x > 1: > return f(x-1) ** x > elif x == 1: > return 10 > else: > raise ValueError > return len(str(f(x))) -1 > > The great part about this recursive solution is that you don't have to worry > about the stack limit because performance degrades so quickly on the > conversion to string! fact(8) takes a little less than a second, fact(9) > takes about a minute, and fact(10) takes more time than I had patience to > wait for!
And the not-so-great part is that it raises an exception on fact(0) which makes it utterly useless for calculating combinations of m things taken n at a time: m!/n!*(m-n)! Why is it that no one seems able to get this right? > > Cheers, > Cliff -- http://mail.python.org/mailman/listinfo/python-list
