[Dev-luatex] A few newbie questions

Yue Wang yuleopen at gmail.com
Thu Jan 29 05:18:34 CET 2009

> an other issue is that patching whatever bit of tex coude should be done
> very careful; this has been proven by adding a backend ... rather strict
>  control over extensions and changes is needed in order to keep tex's
> reputation of stability up; a one line change could result in for instance a
> rounding issue (i mention it because we ran into it some time ago) and can
> have rather drastic consequences; you don't want that to happen with a
> machinery that has to reproduce a document at the pixel level
> a patch that might work on ones machine might eventually result in many
> problems all over the world if only because most users don't update
> frequently and depend on formal distributions (btw the same is true for
> fonts and other resources ... small changes can have huge consequences)

>From my experience LuaTeX's result is very different from pdfTeX's
result. The most notable one is that they give me different line
breaks even with the same source and tfms given. Last time I was
working on a Chinese translation of Karl's TeX for the Impatients, It
occured to me that LuaTeX's linebreak is so different from pdfTeX's,
and what's worse, LuaTeX gives me more overfull boxes. Of course, I
use an old version of LuaTeX distributed in TeXLive 2008 (0.25.x, if
memory serves). I doubt whether it will be possible for LuaTeX to
produce the similar result as TeX does, (not to say pixel level).

But is compactability that important? XeTeX is not compatible with the
good old TeX, but it is still widely used in Asia (Here we don't use
LuaTeX simply because there is no LaTeX package support). Knuth also
suggested that there are several rounding flaws in recent version of
TeX that he cannot change it, but he recommended that modern
implementations change that (see TUGBoat, Volume 29 (2008) No.2).

Yue Wang

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