Have you tried using define-syntax-class to define some of the "intermediate chunks"?
For example would it help if you were to define a syntax class for old-date, another for time-of-day, and compose old-timestamp from those? On Mon, Jan 21, 2013 at 3:04 PM, Lorenz Köhl <rainbowtw...@gmail.com> wrote: > How can I match datums more concisely with syntax-parse? > > I get syntax objects like this from ragg: > > #'(old-timestamp (old-date 2 23) (time-of-day 2 ":" 23 ":" 42)) > > The parts I care about are the numbers. I write patterns like > > ((~datum old-timestamp) > ((~datum old-date) month day) > ((~datum time-of-day) hour ":" minute ":" second)) > > to extract them. But with longer syntax the patterns gets messy. I tried > #:literals (foo ..) but I don't know what binding I should give to the ids > and how (and why). > > Is there an equivalent to #:datums (old-timestamp time-of-day …) in > syntax-parse? > > Longer example: > > ;; timestamp-stx->list : Syntax -> (Listof Number) > (define (timestamp-stx->list stx) > (define-syntax-rule (! s) > (syntax->datum s)) > > (syntax-parse stx > ;#:literals (old-timestamp old-date time-of-day new-timestamp new-date) > [((~datum old-timestamp) > ((~datum old-date) month day) > ((~datum time-of-day) hour ":" minute ":" second)) > > (list (! #'second) (! #'minute) (! #'hour) (! #'day) (month->num (! > #'month)))] > > [((~datum new-timestamp) > ((~datum new-date) year "-" month "-" day "T") > ((~datum time-of-day) hour ":" minute ":" second)) > 1])) > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
