the point of REC , was (Re: [Chicken-users] Re: crazy behaviour in csi!)

[Sunnan]

On Mon, 2005-12-05 at 23:54 +0100, Jens Axel Søgaard wrote:
> Sunnan wrote:
> > ;; instead of:
> > (let f ((n (...)))
> >   (if (zero? n) 1
> >       (* n (f (- n 1)))))
> > ;; it's the exact same number of characters!
> 
> Almost - note that REC returns the recursive
> function, so you need to return the function
> in the let:
> 
>    ((let f ((n (...)))
>       (if (zero? n) 1
>           (* n (f (- n 1))))
>       f)
>      (...))

But that does the same thing; the whole expression as such returns the
result of the recursive function in both cases. The recursive function
returned by REC is use-once-and-destroy.
And in chicken, 
((rec (F N) 
      (if (zero? N) 1 
          (* N (F (- N 1))))) (...))

macroexpands to almost the same as 

(let f ((n (...)))
  (if (zero? n) 1
      (* n (f (- n 1)))))

if I recall correctly.
BTW, your example evaluates (...) twice.
AML,
Sunnan