Racket does have 'make-set!-transformer' that allows you to define
syntax that cooperates with 'set!'. I think that might work if you are
defining your own datatype. Have you seen that?
Thanks,
Dave
On 06/30/2015 11:10 AM, Alexey Cherkaev wrote:
Hi Alexander,
Thanks for your reply: I had something similar in mind (maybe I should
check out math/array). I was just wondering if there was something
more Racket-like (it still feels that SRFI is somewhat 'foreign'
hack). And my last question remains: wouldn't it be beneficial to have
such a generalised 'set!' system-wide? I understand that Racket
focusses more on immutable structures, but there are still vectors and
hash-tables which are inherently mutable and still have their niche.
Best regards,
Alexey
On 29 June 2015 at 18:36, Alexander D. Knauth <alexan...@knauth.org
<mailto:alexan...@knauth.org>> wrote:
On Jun 29, 2015, at 5:56 AM, Alexey Cherkaev
<alexey.cherk...@gmail.com <mailto:alexey.cherk...@gmail.com>> wrote:
> For example, I was thinking of defining syntax to access my
implementation of multidimensional arrays
> as
>
> (define-syntax aref
> (syntax-rules (set!)
> [(set! (aref ?a ?i ...) ?v) (array-set! ?a ?i ... ?v)]
> [(aref ?a ?i ...) (array-ref ?a ?i ...)]))
>
> but obviously it won't work now as `set!` expects the `id` not
an expression (`syntax-id-rules` won't work either as `aref` is
not an `id`).
#lang racket
(require srfi/17 math/array)
(define (aref a . is)
(array-ref a (list->vector is)))
(set! (setter aref)
(λ (a . is+v)
(match-define (list is ... v) is+v)
(array-set! a (list->vector is) v)))
(define a (mutable-array #[#[1 2] #[3 4]]))
(aref a 0 1)
(set! (aref a 0 1) 20)
(aref a 0 1)
If you wanted, you could also define your own version of set! that
does what you want, which (I think) you would need to do if you
needed aref to be a macro.
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