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Date:         Tue, 13 Oct 2020 20:09:05 +0200
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From:         LARONDE Thierry <tlaronde@POLYNUM.COM>
Subject: Re: LaTeX3 and l3kernel requirements
To:           LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
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Envelope-To: <rainer.schoepf@gmx.net>
Status: R

Hello Joseph,

On Tue, Oct 13, 2020 at 06:44:43PM +0100, Joseph Wright wrote:
> Hello Thierry,
> 
> >The first "engine" modification of LaTeX, a few months ago, was to > request the e-TeX extensions and drop vanilla TeX. OK, done.
> The original announcement about e-TeX was back over 15 years ago :) The
> hyphenation patterns actually stepped things on well before the LaTeX
> kernel. Practically, therefore, it has been necessary for a number of years
> 'in the wild'.
> 
> >1) Is LaTeX3 aimed to be a "TeX" free engine, that is will not run on a
> >TeX (at least a e-TeX) engine in the future?
> 
> New features have been added to engines and there comes a point at which not
> using them uniformly is problematic. There is no 'aim' to set out to use
> particular primitives, rather new primitives offer abilities not available
> in Knuth's TeX or e-TeX. As such, the team have added new required
> primitives to support improved behaviours. As I mention below, these 'new'
> primitives have been around for some time.
> 
> >2) If this step is taken, can you provide on CTAN a latex2e link to the
> >last TeX compatible version (for the moment, latex2e points to the
> >latest latex that is, IIUC, latex3...)?
> 
> LaTeX remains LaTeX2e: there will be no stand-alone LaTeX3. Moreover, CTAN
> holds the latest release, and it would be very tricky if there were a second
> latex.ltx there which conflicted with the release. That said, it is possible
> to arrange to use older kernel files: they are in TeX Live or available for
> the Git repository for LaTeX. Probably we should discuss directly how best
> to arrange this (as you do not build from TL).
> 

In the mean time, I have cloned the 2020-02-02 PL5 and will simply point
the packaging system to the kerTeX server and not for the moment directly
to CTAN (the kerTeX packaging system was indeed always using CTAN
sources so that as long as the installation procedure didn't change,
of the hierarchy was not modified, the "same" pkg didn't need any work
to be able to install the latest release).

This will allow during the time needed to fix the problem (if possible),
for the kerTeX users (not thousands of them but some) to have LaTeX.

> >3) What are the so crucial primitives, not present in TeX or e-TeX,
> >that it is not possible to treat them as possible extensions, been
> >tested against for conditional treatment inclusions, but have to be
> >absolute required ones? If they do exist, and have nothing
> >to do with post-processing that is printing specially in PDF (which
> >should be deferred to post-processing utilities), are there change files
> >to be applied to e-TeX in order to create a special engine meeting your
> >requirements?
> 
> The new required primitives have been in pdfTeX for over 10 years and do not
> directly relate to PDF output. They have been ported to (u)pTeX as part of
> .ch files: pdfTeX itself is a stand-alone .web source. (They have also been
> ported to XeTeX, but again that has a single .web rather than using .ch
> files.) The issue for you is likely to be one of license rather than any
> technical restriction: pdfTeX is GPL. One could certainly start from the
> (u)pTeX .ch file, although it is part of a somewhat complex chain which
> allows building of pTeX and upTeX along with e-pTeX and e-upTeX.

I have already made so much work around the TeX system that I'm not afraid 
anymore to tackle it. I will simply add this to the e-TeX engine
and as long as users have their LaTeX, sufficiently up-to-date,
for now, it can take several weeks or even months.

Can you simply point me to the (u)pTeX .ch file and point me to the
initial documentations/articles that list the primitives
needed and what they have to achieve?

> 
> One reason we have only recently stepped up the primitive requirement was
> precisely to arrange that all 'current' engines (those in TeX Live/MiKTeX),
> other than Knuth's TeX (which will not change), were ready. One primitive
> had already 'slipped through': practically, \ifincsname was already required
> for UTF-8 text to work well, and was delayed as a hard requirement only as
> there was a need for (u)pTeX to 'catch up'.
> 
> >4) Are the modifications so deep that for the hundreds of LaTeX related
> >macros already written, they will have to be rewritten to continue to be
> >compatible with LaTeX3?
> 
> Over time new code will be written to use the new programming layer, and it
> relies on post-e-TeX primitives, most notable \pdfstrcmp. A lot of LaTeX
> packages already use expl3 (the programming language the LaTeX team have
> developed), and so are already not usable even with older LaTeX formats if
> the new primitives are not available.
> 
> I hope this helps: we are cautious about new primitives but cannot avoid the
> fact that engine development has continued since e-TeX was finalised in
> 1999.
> 

Thanks for the clarifications!

Best regards,
-- 
        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
                     http://www.kergis.com/
                http://www.kergis.com/kertex.html
                       http://www.sbfa.fr/
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