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Re: Syntax change proposal:

From: David Kastrup
Subject: Re: Syntax change proposal:
Date: Thu, 19 Jul 2012 15:43:08 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1.50 (gnu/linux)

"Trevor Daniels" <address@hidden> writes:

> David Kastrup wrote Monday, July 16, 2012 9:18 AM
>> Graham Percival <address@hidden> writes:
>>> On Mon, Jul 16, 2012 at 02:02:31AM +0200, David Kastrup wrote:
>>>> One really ugly problem is interpreting things like "4.".  Looks like a
>>>> duration, but then we have
>>>> input/regression/  line-width = 4.\cm
>>> I am against making a change like this outwith[1] of GLISS.  It
>>> could involve a lot of user pain (and documentation-editing
>>> pain!), so I think it's important to at least pretend[2] to have
>>> good user consultation beforehand.
>> I disagree with "a lot of user pain".
>>> As far as the actual proposal goes, I'm generally in favor.
> [snip a long convincing argument]
> I'm generally in favour too, but I'd be happier if this were deferred
> until 2.17.

Well, let's see what the parser currently delivers in INITIAL mode.

.     character .
-.    REAL 0.0
-.0   REAL -0.0
-0.0  character - followed by 0.0

Now how do we explain that there are contexts where -.3 is a valid REAL
whereas -0.3 isn't?

Or that -. is a REAL with a value different from -.0 whereas . is a

I am not convinced that this is an area that's really good for keeping.
The semantics of -., for example, were introduced in 2.15.9 with

commit da949cdcede0ffb559e9e5e2adbae2088ba1f6d6
Author: Keith OHara <address@hidden>
Date:   Wed Aug 10 00:57:44 2011 -0700

    lexer.ll: remove unused patterns, avoid backing up

so it is not like stable release users rely on them.  While most is
older than that, I am not overly impressed with it either.

David Kastrup

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