Hi all,
Ekaitz Zarraga <eka...@elenq.tech> writes:
> From ab6e4980ea301b5d1e14a98464e5de3e726984f1 Mon Sep 17 00:00:00 2001
> From: Ekaitz Zarraga <eka...@elenq.tech>
> Date: Mon, 7 Aug 2023 20:23:42 +0200
> Subject: [PATCH] fix cond1 macro
Just adding some context, as we talked about this on IRC.
If you take the docs example as is,
(define-syntax cond1
(syntax-rules (=> else)
((cond1 test => fun)
(let ((exp test))
(if exp (fun exp) #f)))
((cond1 test exp exp* ...)
(if test (begin exp exp* ...)))
((cond1 else exp exp* ...)
(begin exp exp* ...))))
and invoke it as
(cond1 else #t)
you get
Syntax error:
unknown location: else: bad use of 'else' syntactic keyword in
subform else of else
This is because ‘else’ matches the ‘(cond1 test exp exp* ...)’ pattern
and gets inserted as the test:
(if else (begin #t))
This patch puts the more specific ‘else’ pattern before the more general
‘test’ pattern so it has a chance to be matched.
-- Tim
