I'm in no ways a macro expert, but will this work? It uses identifier-binding
to check if the identifier for the hash table is bound.
(define-syntax (set/define stx)
(syntax-case stx ()
[(_ ht key value)
(cond [(identifier-binding #'ht)
#'(hash-set! ht key value)]
[else
#'(begin
(define ht (make-hash))
(hash-set! ht key value))])]))
On Friday, April 19, 2019 2:33:54 PM PDT zeRusski wrote:
> Not quite what I had in mind. The following examples must all work without
> errors:
>
> #lang racket
>
> ;; set/define defined here
>
> (set/define h a 1)
> (set/define h a 2)
> (hash-set! h 'b 42)
>
> (define bar (make-hash))
> (set/define bar a 1)
>
> (define (foo)
> (set/define local-h a 1)
> (set/define local-h a 2)
> (hash-set! local-h 'b 42)
> local-h)
>
> (foo)
>
> Basically, if the identifier h is unbound at runtime
> (set/define h key val)
> is the same as
> (define h (make-hash))
> (hash-set! h 'key val)
>
> If h is bound
> (hash-set! h 'key val)
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
