Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!ucbvax!bloom-beacon!eru!hagbard!sunic!mcsun!hp4nl!ruuinf!piet
From: piet@cs.ruu.nl (Piet van Oostrum)
Newsgroups: comp.text.tex
Subject: Re: inconsistency between TeX 2.9 and 3.0
Message-ID: <3912@ruuinf.cs.ruu.nl>
Date: 27 Sep 90 12:01:55 GMT
References: <1990Sep27.010730.1819@zaphod.mps.ohio-state.edu>
Sender: news@ruuinf.cs.ruu.nl
Reply-To: piet@cs.ruu.nl (Piet van Oostrum)
Organization: Dept of Computer Science, Utrecht University, The Netherlands
Lines: 35
In-reply-to: eao@shape.mps.ohio-state.edu (Ed Overman)

>>>>> In article <1990Sep27.010730.1819@zaphod.mps.ohio-state.edu>, eao@shape.mps.ohio-state.edu (Ed Overman) (EO) writes:

EO> We just installed TeX 3.0 here over the weekend and there seems to be
EO> an inconsistency between the new and old versions.  I get different
EO> results with the following:

[ Example replaced by the following simpler:]

\if\par\% TRUE\else FALSE\fi

The TeX3.0 behaviour is the correct one. Both \par and \% are not
expandable (they are not macros or anything mentioned on page 213/214)

So they are considered to have character codes 256 and thus to test equal.

Tex 2.9 and previous versions had a bug whereby \par was considered to have
character code 0 (and category code 13).
So the following example erroneously came out with TRUE:

\catcode`\%=13
\ifcat\par\noexpand%TRUE\else FALSE\fi


The fix is described in errorlog.tex:
------------------------------------------------------------------------
* 3 Dec 1989
...
S893. Distinguish |\par| from characters on |\if| tests. (MVL). @334
------------------------------------------------------------------------
(that's a strange way of saying it!)
-- 
Piet* van Oostrum, Dept of Computer Science, Utrecht University,
Padualaan 14, P.O. Box 80.089, 3508 TB Utrecht, The Netherlands.
Telephone: +31 30 531806   Uucp:   uunet!mcsun!ruuinf!piet
Telefax:   +31 30 513791   Internet:  piet@cs.ruu.nl   (*`Pete')