From b1506c8083c5d55aa8dc1350a0ca1aea924be4b4 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Thu, 3 Sep 2020 15:28:14 +0100
Subject: [PATCH] mdwtab.dtx: Fix nested `*' column-type to work correctly.

This is a little unpleasant.
---
 mdwtab.dtx | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/mdwtab.dtx b/mdwtab.dtx
index 15e2988..03e7866 100644
--- a/mdwtab.dtx
+++ b/mdwtab.dtx
@@ -44,7 +44,7 @@
 %<+color>                [2003/08/24 1.10 Fix for people who can't spell]
 % \end{meta-comment}
 %
-% \CheckSum{3402}
+% \CheckSum{3421}
 %% \CharacterTable
 %%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
 %%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
@@ -2725,16 +2725,30 @@
 \coldef ##1#2{\tabcoltype{#1}{#2}}
 %    \end{macrocode}
 %
-% And \lit{*}, which repeats a preamble spec.  This is really easy, and not
-% at all like the original one.
+% And \lit{*}, which repeats a preamble spec.  The tricky part is ensuring
+% that nested \lit{*} specs work correctly: we must save the loop counter, in
+% |\count 0|, obviously, but \emph{also} the |\iterate| macro built which
+% |\loop| modifies internally.  Usually you'd use grouping to fix this, but
+% if we introduce a group level then we won't update the preamble registers
+% correctly.  Instead, queue up tokens to restore the values in \TeX's input
+% list.
 %
 %    \begin{macrocode}
 \coldef *#1#2{%
-  \count@#1%
-  \loop\ifnum\count@>0\relax%
-    \tab@doreadpream{#2}%
-    \advance\count@\m@ne%
-  \repeat%
+  \toks\tw@\expandafter{\iterate}%
+  \toks@{%
+    \count@#1%
+    \loop\ifnum\count@>0\relax%
+      \tab@doreadpream{#2}%
+      \advance\count@\m@ne%
+    \repeat%
+  }%
+  \edef\@tempa{%
+    \the\toks@%
+    \def\noexpand\iterate{\the\toks\tw@}%
+    \count@\the\count@%
+  }%
+  \@tempa%
 }
 %    \end{macrocode}
 %
-- 
2.11.0