Untested but I think this will work
(define-syntax (my-macro stx)
(syntax-case stx ()
[(_ (id1 id2 ...) body ...)
#'(lambda (expr)
(match expr [(list 'id1 id2 ...) body ...]))]))
On 01/15/2013 10:22 PM, Paul Meier wrote:
> Hi friends,
>
> I'm working on a macro that expands into a match statement. It looks
> something like
>
> (define-syntax (my-macro stx)
> (syntax-case stx ()
> [(_ (id1 id2 ...) body ...)
> (with-syntax ([match-pattern
> (datum->syntax stx (cons 'list (syntax->datum
> #'(id1 id2 ...))))])
> #'(lambda (expr)
> (match expr
> [match-pattern body ...])))))
>
> So in effect, it expands
>
> (my-macro (push i) (printf "~v" i)
>
> into
>
> (lambda (expr)
> (match expr
> [(list push i) (printf "~v" i)]))
>
> Here is the problem: I'd like the first entry of the match list to be quoted
> (e.g. 'push) rather than unquoted, as it is above, since 'match' will
> interpret this as a free variable, meaning
>
> ((my-macro (push i) i) '(dont-push 45)) will evaluate to 45, rather than fail
> to match (the desired behavior).
>
> Unfortunately, trusty (quote (syntax->datum stx id1)) and or any variation
> thereof will do what it's supposed to: quote whatever expression will
> evaluate into whatever I want quoted.
>
> I could just write the quotes into the expressions using the macro, a la
> (my-macro ('push i) ...), but Shirly there's a way around this?
>
> Any help would be appreciated. Thanks for your time; I'm loving my
> explorations into Racket ^_^
>
> -Paul
>
>
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