On Aug 6, 2014, at 1:10 PM, Kevin Forchione <[email protected]> wrote:
> > On Aug 5, 2014, at 2:21 PM, Jens Axel Søgaard <[email protected]> wrote: > >> Is this a step in the right direction? >> >> (define-syntax (x stx) >> (syntax-parse stx >> [(_ (y ... (z ...) w ...)) >> #'(xf (yf y ... (zf z ...) w ...))])) >> >> The pattern (z ...) ... will match a sequence of lists such as (4 5 6) (7 8) >> but it won't match (4 5 6) 7 8 from your example. >> >> /Jens Axel > > Closer. It doesn’t match something like ‘( 1 2 3 (4 5 6) 7 (8 9) 10), for > instance. For that I think you want something like this: (syntax-parse stx [(_ (~or (z ...) y) ...) #'(xf (yf y ... (zf z ...)))]) Either that or you can use my version of syntax-parse with pattern-expanders and use ~seq-no-order: https://github.com/AlexKnauth/seq-no-order > > I have tried: > > #lang racket > > (require (for-syntax syntax/parse)) > > (define-syntax (x stx) > > (define-syntax-class binding > #:description "binding list" > (pattern (z:id ...))) > > (define-syntax-class or-binding > #:description "binding or" > (pattern (~or zb:binding y:id) > #:with (z ...) #'(zb.z ...))) This won’t work because if the y:id pattern matches instead of the zb:binding pattern, then the zb.z attribute won’t be there. Instead you probably wan’t this: (define-syntax-class or-binding #:description "binding or" (pattern zb:binding #:with (z ...) #'(zb.z ...)) (pattern y:id #:with (z ...) #'(y)) ; or whatever, depending on what you want to do here ) > > (syntax-parse stx > [(_ (ob:or-binding ...) ...) > #''ok > #;#'(xf (yf ob.y ...) ...) > #;#'(xf (yf ob.y ... (zf ob.z ...) ...) ...)])) > > (define (xf . xs) xs) > (define (yf . ys) ys) > (define (zf . zs) zs) > > (x (a)) > (x (a b (c))) > (x (a b c (d e f) g h)) > > But while the pattern “appears” to match, I can’t seem to construct a > template that is acceptable to syntax-parse, which doesn’t like the #:with > clause on my syntax-class or-binding. I must be missing something. > > -Kevin > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users
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