Hi guys,
I’ve been working with Racket 6.5 refreshing my macro knowledge and ran into a
situation with format-id that baffles me. There’s an example of format-id on
the “Fear of Macros” webpage that puzzles me.
>(require (for-syntax racket/syntax))
>(define-syntax (hyphen-define/ok3 stx)
(syntax-case stx ()
[(_ a b (args ...) body0 body ...)
(with-syntax ([name (format-id stx "~a-~a" #'a #'b)])
#'(define (name args ...)
body0 body ...))]))
>(hyphen-define/ok3 bar baz () #t)
>(bar-bas)
#t
So far so good… so I tried a few other arguments:
>(hyphen-define/ok3 bar ? () #t)
>(bar-?)
#t
>(hyphen-define/ok3 bar 7 () #t)
>(bar-7)
../../Applications/Racket v6.5/collects/racket/private/map.rkt:26:19:
format-id: contract violation
expected: (or/c string? symbol? identifier? keyword? char? number?)
given: #<syntax:16:23 7>
That was a surprise. So ids can’t have numerics as part of their arguments in
format-id? Is that correct? How would I make this work if I wanted to pass
numbers into the format-id to generate ids like foo7, bar3, etc?
Thanks so much for any insight into this!
-Kevin
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