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Re: [patch] variable datums with syncase transformer
From: |
Ludovic Courtès |
Subject: |
Re: [patch] variable datums with syncase transformer |
Date: |
Wed, 05 Mar 2008 17:34:26 +0100 |
User-agent: |
Gnus/5.11 (Gnus v5.11) Emacs/22.1 (gnu/linux) |
Stephen Compall <address@hidden> writes:
> address@hidden (Ludovic Courtès) writes:
>> OTOH, you can (should?) use `use-modules':
>> <snip>
>>
>> I don't even understand what the difference is between using
>> `use-modules' and `use-syntax' for `(ice-9 syncase)'.
>
> guile> (use-modules (ice-9 syncase))
> guile> (define-syntax x-of-y
> (lambda (stx)
> (syntax-case stx ()
> (_ (syntax (hashq-ref y 'x))))))
> guile> x-of-y
> #<macro! sc-macro>
>
> ;;restart
> guile> ;;same as above, using use-syntax instead
> guile> x-of-y
>
> Backtrace:
> In unknown file:
> ?: 0* [hashq-ref ...
Oh, forgive my ignorance, I didn't know `syntax-case' allowed non-list
patterns. It makes me like syntax transformers a bit more. ;-)
Getting back to your initial problem...
> guile> (use-syntax (ice-9 syncase))
> guile> (@ (guile) car)
> ERROR: invalid syntax #<variable b7c50a40 value: #<primitive-procedure car>>
Note that `@' and `@@' rely on an interesting property of the evaluator:
you type `(@ (guile) car)', `@' returns a *variable*, but what you get
is a *procedure*, because in the meantime, the evaluator automagically
performed a `variable-ref'. This is not very elegant in my opinion.
With that in mind, I propose instead the following patch, which also
fixes your problem AFAICS:
--- /home/ludo/src/guile/1.8/guile-core/ice-9/boot-9.scm.~1.356.2.10.~
2007-09-01 19:11:00.000000000 +0200
+++ /home/ludo/src/guile/1.8/guile-core/ice-9/boot-9.scm 2008-03-05
17:25:15.000000000 +0100
@@ -2988,7 +2988,7 @@
(let ((var (module-variable (resolve-interface mod-name) var-name)))
(if (not var)
(error "no such public variable" (list '@ mod-name var-name)))
- var))
+ (variable-ref var)))
;; The '@@' macro is like '@' but it can also access bindings that
;; have not been explicitely exported.
@@ -2997,7 +2997,7 @@
(let ((var (module-variable (resolve-module mod-name) var-name)))
(if (not var)
(error "no such variable" (list '@@ mod-name var-name)))
- var))
+ (variable-ref var)))
Would it be OK for you?
Thanks,
Ludovic.