[tex-hyphen] hyphenation different in xelatex?

[Reinhard Kotucha]

On 2015-09-07 at 19:04:31 +0200, Élie Roux wrote:

 > So it's all based on definitions: yes, documents written with TeX82
 > primitives should probably compile with the TeX82 engine, and the
 > "tex" command privided by TeXLive should probably be something 100%
 > compatible with the TeX82 engine (is it even the case? I'm not sure
 > it may include some evil eTeX primitives!). But is "TeX" the TeX82
 > engine? I don't think so...

TeX Live provides TeX 3 with the original hyphenation patterns (US
English only) and without etex primitives.  It's exactly the program
provided and maintained by DEK.  The executable is called "tex".

If you need etex primitives and/or hyphenation patterns you have to
use another engine.  As you can see on Unix systems, most "engines"
are just symlinks to pdftex (which is actually pdfetex), but "tex" is
definitely and deliberately a separate program.  And pdftex is 100%
backwards compatible with DEK's TeX.

I suppose that TeX 3 is 100% downwards compatible with TeX82.
Phil, can you confirm?

 > So I don't think such inherent caracteristics about TeX exist,
 > [...]

At least for TeX itself (not LaTeX) "The TeXbook" is the definite
specification, and if something is unclear there, you can consult
"TeX: The Program".  Nothing is better documented than TeX.

 > For me (and 99% of "TeX" users, though not for people on this list
 > I'm sure) TeX is a kind of odd language with many different
 > implementations and ecosystems with which you can produce PDFs.

I obviously miss your point.  We have two new engines which are not
stable yet (version number < 1) and there is no problem if new
features are added to them, even if they lead to other results.  Why
should one want to add these features to old engines?  There is no
reason to do so.

Similarly I hope that LaTeX 3 will not inherit all the bugs LaTeX~2e
inherited from LaTeX 2.09.  Both systems can be used side-by-side.

What do 99% of TeX users expect?  I can assure you that they are not
willing to adopt all their files whenever they update their TeX Live
system.  They expect stability.  Definitely!

Regards,
  Reinhard

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