[racket users] Detecting characters in symbols in macros

[Kevin Forchione]

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

[Sam Tobin-Hochstadt]

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

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