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From: Andy Wingo <wingo@pobox.com>
To: ludo@gnu.org (Ludovic Courtès)
Cc: guile-devel@gnu.org
Subject: Re: pending branch: lexical-literals
Date: Fri, 06 May 2011 19:39:34 +0200	[thread overview]
Message-ID: <m339kr919l.fsf@unquote.localdomain> (raw)
In-Reply-To: <871v0cja5p.fsf@gnu.org> ("Ludovic Courtès"'s message of "Fri, 06 May 2011 14:17:22 +0200")

On Fri 06 May 2011 14:17, ludo@gnu.org (Ludovic Courtès) writes:

> Sorry for the late reply.

No prob; thanks for thinking through it!

> So, with this change, no top-level binding of ‘else’ is /required/, but
> /when/ there is one, it prevails over the literal, correct?

Sorta?  This language is imprecise.  The real language is in R6RS: 

    The free-identifier=? procedure returns #t if and only if the two
    identifiers would resolve to the same binding if both were to appear
    in the output of a transformer outside of any bindings inserted by
    the transformer. (If neither of two like-named identifiers resolves
    to a binding, i.e., both are unbound, they are considered to resolve
    to the same binding.)

Nothing changes in the case that `else' is unbound always.

The change is if it is bound when the macro is defined, but not when it
is used, or vice versa; or, also, if it is bound at both places, but to
different lexical or toplevel variables.  In these cases the
lexical-literals branch causes the literals not to match.

OTOH currently a keyword imported under a different name will not match
itself; this branch allows renaming keywords.

> But then I don’t understand how the story that you could import/rename
> ‘else’ fits into this.

I guess basically the summary is "compare literals by identity, not by
name".

Andy
-- 
http://wingolog.org/



  reply	other threads:[~2011-05-06 17:39 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-29 15:16 pending branch: lexical-literals Andy Wingo
2011-05-06 12:17 ` Ludovic Courtès
2011-05-06 17:39   ` Andy Wingo [this message]
2011-06-30 11:46 ` Andy Wingo

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