* Is it possible to expand syntax inside match?
@ 2021-10-24 6:49 Михаил Бахтерев
2021-10-24 19:48 ` Maxime Devos
0 siblings, 1 reply; 2+ messages in thread
From: Михаил Бахтерев @ 2021-10-24 6:49 UTC (permalink / raw)
To: guile-user
Greetings!
I wondering, if is it possible to implement something like
this?
(define-syntax R (syntax-rules () ((_ r v l) #(red r v l))))
(define-syntax B (syntax-rules () ((_ r v l) #(black r v l))))
(define red-black-set-balance
(match-lambda
((or (B (R (R a x b) y c) z d)
(B (R a x (R b y c)) z d)
(B a x (R (R b y c) z d))
(B a x (R b y (R c z d)))) (R (B a x b) y (B c z d)))
(node node)))
The idea is to have some automation allowing not to write
patterns manually:
#('black #('red #('red a x b) y c) z d)
- Mikhail Bakhterev, respectfully.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Is it possible to expand syntax inside match?
2021-10-24 6:49 Is it possible to expand syntax inside match? Михаил Бахтерев
@ 2021-10-24 19:48 ` Maxime Devos
0 siblings, 0 replies; 2+ messages in thread
From: Maxime Devos @ 2021-10-24 19:48 UTC (permalink / raw)
To: Михаил Бахтерев,
guile-user
Михаил Бахтерев schreef op zo 24-10-2021 om 11:49 [+0500]:
> Greetings!
>
> I wondering, if is it possible to implement something like
> this?
>
> (define-syntax R (syntax-rules () ((_ r v l) #(red r v l))))
> (define-syntax B (syntax-rules () ((_ r v l) #(black r v l))))
>
> (define red-black-set-balance
> (match-lambda
> ((or (B (R (R a x b) y c) z d)
> (B (R a x (R b y c)) z d)
> (B a x (R (R b y c) z d))
> (B a x (R b y (R c z d)))) (R (B a x b) y (B c z d)))
> (node node)))
Not exactly what you were looking for, but maybe use quasisyntax /
unsyntax #` #, something like (untested):
;; define, not define-syntax!
(define R (syntax-rules () ((_ r v l) #(red r v l))))
(define B (syntax-rules () ((_ r v l) #(black r v l))))
(define-syntax red-black-set-balance-m
(lambda (s)
#`(match-lambda
((or #,(B (R (R a x b) y c) z d)
#,(B (R a x (R b y c)) z d)
...))
(node node))))
(define red-black-set-balance red-black-set-balance-m)
Greetings,
Maxime
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