Iteration for Factorials

[Steven Bethard]

Michael J. Fromberger wrote:
>   # Not legal Python code.
>   def fact3(n, acc = 1):
>     TOP: 
>       if n > 0
>         n = n - 1
>         acc = acc * n
>         goto TOP
>       else:
>         return acc

Yes, to write this in legal Python code, you have to write::

   from goto import goto, label # http://entrian.com/goto/

   def fact3(n, acc = 1):
     label .TOP
     if n > 0
       n = n - 1
       acc = acc * n
       goto .TOP
     else:
       return acc

;-)

STeVe

> 
> Naturally, of course, Python does not provide a "goto" statement.  But 
> it does have one that's similar:
> 
>   while TEST: BODY
> 
> is equivalent in meaning to the pseudo-code:
> 
>   X: if TEST: 
>        BODY  
>        goto X
> 
> Can you now see how you would re-write "fact3" into legal Python code,
> using this equivalence?  Once you have done so, you will also be able to
> get rid of the extra accumulating parameter, and then you will have what 
> you wanted.
> 
> I hope this helps.
> 
> Cheers,
> -M
>