Is it possible to expand syntax inside match?

Is it possible to expand syntax inside match?

[Михаил Бахтерев]

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.

Re: Is it possible to expand syntax inside match?

[Maxime Devos]

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