Here's an example:
#lang racket
(require (for-syntax syntax/parse))
(define-syntax (foo stx)
(syntax-parse stx
[(_ arg:id)
#:when (regexp-match "[$]" (symbol->string (syntax-e #'arg)))
#'1]
[(_ arg) #'2]))
(foo $abc)
(foo abc)
That prints 1 followed by 2.
Sam
On Wed, Dec 9, 2020 at 12:29 PM Kevin Forchione wrote:
>
> Hi guys,
> Is there a way to detect a character in a symbol in a macro so that one
> branch of the syntax-parse would be chosen or discarded based on that?
>
> Here’s roughly what I’m getting at….
>
> #lang racket
>
> (require (for-syntax syntax/parse))
>
> (define-syntax (foo stx)
> (syntax-parse stx
> [(_ arg) #'(do-$ arg)]
> [(_ arg) #'(do-other arg)]))
>
> (foo $abc)
> (foo abc)
>
> I was thinking expo/c might come into play here, but maybe there’s another
> approach?
>
> Thanks!
>
> Kevin
>
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