Re: [Chicken-users] How to structure a project

[felix winkelmann]

On 1/10/07, Graham Fawcett <address@hidden> wrote:
> On 1/10/07, Zbigniew <address@hidden> wrote:
> > Apropos of nothing, if you surround the body of FAC with (let ((fac
> > fac)) ...) or even (let loop ((n n)) ...) then you avoid a global
> > lookup on FAC on every recursive call.  This is the same as compiling
> > the file in block mode, except the latter doesn't work for exported
> > definitions.  This is something most people here probably know, but
> > it's an interesting optimization trick that took me a while to come
> > across.
>
> Thanks, Zbigniew -- I had never thought to do that. :-)
> A macro comes to mind:
>
> (define-macro (define/rec sig . body)
>   (let ((name (car sig)))
>     `(define (,name ,@(cdr sig))
>        (let ((,name ,name))
>          ,@body))))
>
> (macroexpand '(define/rec (fac n) (if (zero? n) 1 (* n (fac (- n 1))))))
> => (##core#set! fac (lambda (n) (let ((fac fac)) (if (zero? n) 1 (* n
> (fac (- n 1)))))))

The historical MacScheme compiler (and possibly Larceny) actually
have an optimization option ("benchmark-mode") that makes this
the default behaviour of "define".


cheers,
felix