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]))
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