Mark H Weaver <[email protected]> skribis:
> [email protected] (Ludovic Courtès) writes:
[...]
>> Actually my question was more about the ellipsis escaping form
>> (... ...). It is affected by ‘with-ellipsis’, right?
>
> Yes, so the following works:
>
> (define-syntax define-inline
> (with-ellipsis ---
> (syntax-rules ()
> ((_ (name parms ---) exp ---)
> (define-syntax name
> (with-ellipsis (--- ---)
> (syntax-rules ()
> ((_ args (--- ---))
> ((lambda (parms ---) exp ---)
> args (--- ---))))))))))
Sorry I wasn’t clear. Does this work:
(define-syntax define-inline
(with-ellipsis ---
(syntax-rules ()
((_ (name parms ---) exp ---)
(define-syntax name
(with-ellipsis --- ; <- note here!
(syntax-rules ()
((_ args (--- ---))
((lambda (parms ---) exp ---)
args (--- ---))))))))))
IOW, does the escaping syntax adjust to the current ellipsis?
> Needless to say, the whole point of custom ellipses is to avoid having
> to ever escape ellipses, but you can still do it.
Yes of course; that’s an academic question to satisfy my curiosity.
>>> Note that as currently implemented, the effect of 'with-ellipsis'
>>> also does not propagate into nested syntax definition forms such as
>>> 'let-syntax', 'letrec-syntax', and 'define-syntax'. We could go either
>>> way on this.
>>
>> Well, I think it’s fine this way, but then again I’ve been living in
>> world without that feature. ;-)
>>
>> How does R7RS syntax-rules behave in that respect? I guess we should
>> just follow suit.
>
> In R7RS, custom ellipsis is not part of the lexical environment, and
> thus does not propagate at all. A custom ellipsis affects only the
> patterns and templates of the 'syntax-rules' macro it is passed to.
>
> I ended up making the effect of 'with-ellipsis' propagate into syntax
> definition forms, since the semantics seem simpler to me.
OK.
So does that mean that in the example above the second ‘with-ellipsis’
can now be omitted, or is it limited to ‘let...-syntax’?
> I pushed this and the 'syntax-error' patch to stable-2.0.
Great, thank you!
Ludo’.
