From 594a9d1f1ba306b36e7d5f9ffa79315fd3fe8601 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= Date: Thu, 14 Jan 2010 19:35:31 +0100 Subject: Add documentation to regs. --- luatexbase-regs.dtx | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'luatexbase-regs.dtx') diff --git a/luatexbase-regs.dtx b/luatexbase-regs.dtx index e93d57f..14242a1 100644 --- a/luatexbase-regs.dtx +++ b/luatexbase-regs.dtx @@ -129,10 +129,43 @@ and the derived files % \maketitle % % \begin{abstract} +% This package extends the register allocation scheme of Plain~\TeX\ and +% \LaTeX\ to take advantage of the increased number of registers available in +% \LuaTeX. % \end{abstract} % % \section{Documentation} % +% Since the Plain~\TeX\ and \LaTeX\ formats are both frozen, they fail to take +% into account the extended resources provided by newer \TeX-like engines. +% This package focuses on the allocation scheme for registers. \TeX82 provides +% $6$ kinds or registers: count, dimen, skip, muskip, box and toks and has +% $256$ registers of each kind. \eTeX\ and most of its descendants add one +% kind of register (marks) and offers $2^{15} = 32768$ of each kind. \LuaTeX\ +% provides $2^{16} = 65536$ registers of each kind. (It also provides new +% register-like resources, but this package addresses only the resources +% inherited from \eTeX.) +% +% More precisely, \textsf{luatexbase-regs} loads the \textsf{etex} package (or +% makes sure it is preloaded in the format) and then adapts it to the new +% limits of \LuaTeX. Thus, all macros defined by the \textsf{etex} package are +% made available (most notably, \verb+\loccount+, \verb+\globcountblk+, +% \verb+\loccountblk+ and alike). However, if a register of some kind has been +% locally allocated before this package is loaded, then the number of +% allocatable registers of this kind will not be extended to $65536$. To avoid +% this, load \textsf{luatexbase-regs} earlier. +% +% The Plain~\TeX\ and \LaTeX\ formats define a new kind of resource: +% \emph{inserts} which are merely a family (count, dimen, skip, box) of +% registers with the same number. Inserts allocation begins at $255$ and goes +% toward $0$. Thus we can make room for more inserts by making allocation of +% count-, dimen-, skip- and box-registers start from $256$. With real \eTeX, +% it may be a bad idea since registers with index greater than $256$ have +% degraded performance due to implementation details, but with \LuaTeX the +% performance is uniform, so we just do it. +% +% \clearpage +% % \section{Implementation} % % \begin{macrocode} -- cgit v1.2.3