From: Mark H Weaver <mhw@netris.org>
To: Andy Wingo <wingo@pobox.com>
Cc: 38236@debbugs.gnu.org
Subject: bug#38236: R7RS reader does not support datum labels
Date: Mon, 18 Nov 2019 10:10:30 -0500 [thread overview]
Message-ID: <87ftil5if2.fsf@netris.org> (raw)
In-Reply-To: <87pnhrmtrc.fsf@pobox.com> (Andy Wingo's message of "Sat, 16 Nov 2019 21:49:27 +0100")
Hi Andy,
Andy Wingo <wingo@pobox.com> writes:
> R7RS defines a lexical feature called "datum labels"; see section 2.4 in
> the report. An example would be:
>
> #0=(a b c . #0#)
>
> Guile's reader doesn't support this feature and it's not clear if we
> should, in general.
FYI, I already implemented R7RS datum labels on the 'r7rs-wip' branch
(not to be confused with your new 'wip-r7rs' branch):
https://git.savannah.gnu.org/cgit/guile.git/commit/?h=r7rs-wip&id=92408ac20e921583b8e4ee26463dc5805ef01153
It depends on the preceding commit on the same branch:
https://git.savannah.gnu.org/cgit/guile.git/commit/?h=r7rs-wip&id=f687871eceb94bded109569880e696d8862d84fd
There was also a later commit on that branch that enabled compilation of
cyclic literals, but it's no longer applicable to the 'master' branch.
> Note, datum literals appear to be incompatible with array literals.
Can you elaborate on why you believe they're incompatible? I haven't
looked closely in a while, but I didn't see any incompatibility when I
implemented this before. Datum labels have '#' or '=' after the
numeral, and I'm not aware of any Guile array syntax that does.
I'm also a bit puzzled why you're apparently planning to rewrite
everything I already did on the 'r7rs-wip' branch. The main issue on
that branch is that the implementation of *writing* cyclic data turned
out to be a mess, but it could be removed or replaced without affecting
much else.
Mark
next prev parent reply other threads:[~2019-11-18 15:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-16 20:49 bug#38236: R7RS reader does not support datum labels Andy Wingo
2019-11-16 22:41 ` John Cowan
2019-11-18 15:10 ` Mark H Weaver [this message]
2019-11-18 18:35 ` Andy Wingo
2019-11-18 20:57 ` Arne Babenhauserheide
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