[R6RS] Re: Zapping SET-CAR! & SET-CDR!
Mon Oct 18 13:38:41 EDT 2004
>>>>> "Manuel" == Manuel Serrano <Manuel.Serrano at sophia.inria.fr> writes:
Manuel> I'm strongly against this proposal. In my opinion, mutable
Manuel> pairs is strong characteristic of Lisp. It enables efficient,
Manuel> and sometime simpler, implementation of tree manipulation.
But these could be done with 2-element vectors as well. If you're
concerned about conciseness, you could do
(define (kons x y) (vector x y))
(define (kar x) (vector-ref x 0))
(define (kdr x) (vector-ref x 1))
(define (set-kar! x v) (vector-set! x 0 v))
(define (set-kdr! x v) (vector-set! x 1 v))
Moreover, I would think that the efficiency benefits of having only
immutable pairs would outweight those you cite. Maybe Kent and Will
Manuel> This is because Lisp and Scheme do have side effects on variables and
Manuel> data structures that I have always preferred them to, let's say, CAML.
I like mutable variable bindings as well.
Cheers =8-} Mike
Friede, V?lkerverst?ndigung und ?berhaupt blabla
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