Re: New to the group...

[Ludovic Courtès]

Hi,

"Jason Meade" <address@hidden> writes:

> (define fact
>  (lambda (n)
>    (cond
>     ((= n 1) 1)
>     (else
>      (* n (fact (- n 1)))))))
>
> guile> (fact 69)
> 171122452428141311372468338881272839092270544893520369393648040923257279754140647424000000000000000
> guile> (fact 70)
> ERROR: Stack overflow
> ABORT: (stack-overflow)

Your definition of `fact' is not tail-recursive, i.e., for each
recursive call, a new stack frame is created.  In order to remove this
problem, you have to rewrite `fact' so that it is tail-recursive (which
means that the function returns immediately after the recursive call):
this way Guile will not create any new stack frame for the recursive
calls.

See for instance the definition of `tail-factorial' there:
http://sourceware.org/ml/guile/2000-06/msg00074.html .

Thanks,
Ludovic.