From: Maxime Devos <maximedevos@telenet.be>
To: Zelphir Kaltstahl <zelphirkaltstahl@posteo.de>
Cc: Guile User <guile-user@gnu.org>
Subject: Re: Macro for replacing a placeholder in an expression
Date: Thu, 28 Jul 2022 11:48:58 +0200 [thread overview]
Message-ID: <6a1abc16-7b4d-9ce1-daeb-f908e72c8d4c@telenet.be> (raw)
In-Reply-To: <61f3c2d2-78ec-cec6-5933-f0f8a5bc3aba@posteo.de>
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On 28-07-2022 10:39, Zelphir Kaltstahl wrote:
> I aimed to do everything with syntax-rules, as the simplest means, but
> when writing the code I have, I hit the snag, that one could not have
> multiple ellipses at the same level of nesting in the patterns.
IIUC, you mean:
(syntax-rules ()
((foo x ... y ...) [the replacement]))
? If so, such a construct is ambigious.
> After some thinking I found the solution to build up a temporary list,
> which then is of course 1 deeper level of nesting, where I could then
> use ellipses again. I felt quite clever doing that trick. Maybe I
> could implement a syntax-map using that trick and then use syntax-map
> in my macro instead.
> I have a question regarding syntax-case:
>
> If I use it, does my code become less portable to other Schemes?
>
> And regarding syntax-rules:
>
> How portable are macros, which exclusively use syntax-rules?
>
Everything that supports syntax-case most likely supports syntax-rules
too, as syntax-rules can easily be defined in terms of syntax-case, so
syntax-rules is at least as portable as syntax-case.
syntax-rules and syntax-case are pretty standard (it's in the R6RS), so
I expect them to be available in recent-ish non-minimalistic Schemes.
However, some Schemes (likely Schemes that predate the R6RS, or in
Schemes that try new things out), use other syntax systems.
Anyway, I've found a table:
> https://docs.scheme.org/surveys/syntax-definitions/
Looks like syntax-rules is supported by all the tested systems.
syntax-case is less supported, but among the 'low-level' macro systems
it has the highest support. It's a bit out-of-date though, syntax-case
is supported for Chicken:
http://code.call-cc.org/legacy-eggs/3/syntax-case.html,
Decide for yourself of course, but I don't think going for maximal
portability is worth the effort here of something making things work
with syntax-rules.
>>
>> Greetings,
>> Maxime
>
> Thank you again for your help and explanations! Things are much
> clearer now!
>
> Best regards,
> Zelphir
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next prev parent reply other threads:[~2022-07-28 9:48 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-27 23:57 Macro for replacing a placeholder in an expression Zelphir Kaltstahl
2022-07-28 0:55 ` Maxime Devos
2022-07-28 10:23 ` Zelphir Kaltstahl
2022-07-28 10:28 ` Maxime Devos
2022-07-30 15:42 ` Zelphir Kaltstahl
2022-07-30 20:44 ` Maxime Devos
2022-07-30 21:10 ` Maxime Devos
2022-07-30 21:13 ` Maxime Devos
2022-08-05 9:42 ` Linus Björnstam
2022-08-06 14:28 ` Zelphir Kaltstahl
2022-07-28 1:04 ` Maxime Devos
2022-07-28 8:39 ` Zelphir Kaltstahl
2022-07-28 9:48 ` Maxime Devos [this message]
2022-07-28 11:26 ` Zelphir Kaltstahl
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