I'm trying to write a macro that will turn a list of hex literals into a
byte string.
(hex a b c 1 2 3) ; #"\n\v\f\1\2\3"
After many hours I have finally come up with this:
#lang racket
(define-syntax hex
(syntax-rules ()
[(_ num ...)
(bytes
(let ([e (syntax-e #'num)])
(if (number? e) num
(string->number (symbol->string e) 16))) ...)]))
(hex a b c 1 2 3)
Of course there are many issues with checking the parameters etc. My
problem is this generates "a: unbound identifier in: a" because the
arguments are evaluated? If I remove the last line it works in the REPL OK.
I suspect this is a small matter of my phases being mixed up, or a
misunderstanding of when macros can be defined and used, or just outright
ignorance on my part. I couldn't find any clues in the many, many
references and tutorials I have read. I want to master them but I loathe
creating macros, they always make me feel like an idiot, and I hope Racket2
simplifies them somehow.
Thanks for any help sorting this one out.
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to racket-users+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/racket-users/6d096642-b770-4655-acc5-08b36e176554%40googlegroups.com.
