Factorials

[Tim Rowe]

On Sat, 07 Jun 2003 15:45:37 +0100, Andrew Wilkinson
<ajw126 at NOSPAMyork.ac.uk> wrote:

>The other replies give a much more readable way of getting the factorial,
>but if you're looking for the ultimate in speed then...
>
>def fac(n):
>    return reduce(long.__mul__, range(1,n+1), 1L)

I thought I'd try these out.  Taking Anton's challenging test case of
10000:
- The simple recursive solution runs out of stack space.

- Anton's solution barfs on  R = [x*y for x,y in zip(R[::2],R[1::2])],
complaining that the sequence index must be an integer.

- Yours works fine.

You're winning!

Is it worth mentioning that for all their elegance recursive solutions
are usually /not/ the way to go unless the language is designed for it
-- especially when the solution is tail-recursive and so can be
replaced with a simple loop anyway...