Eric Bavier <ericbav...@openmailbox.org> skribis:
> On Sat, 24 Sep 2016 11:21:40 +0900
> l...@gnu.org (Ludovic Courtès) wrote:
>>
>> > +replaced by EXP. EXP is evaluated in a context where VAR is bound to the
>> > +previous value of the keyword argument, or DFLT if given."
>> > + (syntax-case x ()
>> > + ((_ original-args ((kw var dflt ...) exp) ...)
>> > + #`(let loop ((args (default-keyword-arguments
>> > + original-args
>> > + (list #,@(append-map (match-lambda
>> > + ((k) '())
>> > + (x x))
>> > + #'((kw dflt ...) ...)))))
>> > + (before '()))
>>
>> I would prefer to stick to ‘syntax-rules’ when matching the clauses,
>> with a helper macro:
[...]
> From 9481121fef60f0c3f4ea0f742d77336906771167 Mon Sep 17 00:00:00 2001
> From: Eric Bavier <bav...@member.fsf.org>
> Date: Tue, 20 Sep 2016 15:41:31 -0500
> Subject: [PATCH] utils: Support defaults in substitute-keyword-arguments.
>
> * guix/utils.scm (collect-default-args, expand-default-args): New
> syntax.
> (substitute-keyword-arguments): Allow default value declarations.
> * tests/utils.scm (substitute-keyword-arguments): New test.
[...]
> +(define-syntax collect-default-args
> + (syntax-rules ()
> + ((_ (_ _))
> + (list))
> + ((_ (kw _ dflt))
> + (list kw dflt))
> + ((_ (_ _) rest ...)
> + (collect-default-args rest ...))
> + ((_ (kw _ dflt) rest ...)
> + (cons* kw dflt (collect-default-args rest ...)))))
I think you just need the base case (zero args), the default-value case,
and the no-default-value case:
(define-syntax collect-default-args
(syntax-rules ()
((_) ;done
'())
((_ (kw var) rest ...)
(collect-default-args rest ...))
((_ (kw var dflt) rest ...)
(cons* kw dflt (collect-default-args rest ...)))))
> +(define-syntax expand-default-args
> + (syntax-rules ()
> + ((_ original-args (kw var) ...)
> + original-args)
> + ((_ original-args clause ...)
> + (default-keyword-arguments
> + original-args
> + (collect-default-args clause ...)))))
AFAICS this macro can be removed altogether.
OK with changes along these lines, thanks!
Ludo’.
