Ivan Shmakov wrote:
>>>>>> Sunnan <[EMAIL PROTECTED]> writes:
> > (define (fib)
> > (let loop ((a 1) (b 1))
> > (set! fib (lambda () (loop b (+ a b))))
> > a))
>
> This `set!' isn't necessary, compare:
>
> (define fib
> (let ((a 1) (b 1))
> (lambda ()
> (let ((saved a))
> (set! a b)
> (set! b (+ saved b))
> saved))))
Yes, this is the longer, classic style. As a fib generator with only
two counters, it works fine, but you have to save the entire state "by
hand" with a set! for each original variable, and you also introduce
an extra variable for the "swap". Your version is probably faster, and
probably more familiar to many programmers.
I was just fascinated by the two perverse ideas of
1. freezing a delayed call to a named let
2. resetting/redefining the very function we're in (similar to some
call/cc tricks)
> Both variants should be quite portable. (Especially on
> non-compilers.)
>
Thanks.
Sunnan
_______________________________________________
Chicken-users mailing list
Chicken-users@nongnu.org
http://lists.nongnu.org/mailman/listinfo/chicken-users
