r3tex

commit c0404758eb263369f832e0fe2a83b1afd2747c2c
parent e76fc35a68dcaa49db0cb2d2d411a2b7f3603e86
Author: robert <robertrussell.72001@gmail.com>
Date:   Sat, 15 Jan 2022 12:14:41 -0800

Add \tab, \obeytabs, and \expandtabs macros

Diffstat:
M
param.tex
 | 
1
+
M
r3tex.tex
 | 
1
+
M
util.tex
 | 
21
++++++++++++++++-----

3 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/param.tex b/param.tex
@@ -219,6 +219,7 @@
 	\relax
 
 %%% Custom "parameters":
+% TODO: perhaps some of these should be style-specific
 \newskip\normalbaselineskip
 \newskip\normallineskip
 \newdimen\normallineskiplimit
diff --git a/r3tex.tex b/r3tex.tex
@@ -32,3 +32,4 @@
 
 % TODO: add author info, etc. with \pdfinfo
 % TODO: \author, \title, \date, etc. should parse to eol
+% TODO: \dospecials
diff --git a/util.tex b/util.tex
@@ -16,13 +16,14 @@
 \chardef\#=`\#
 \chardef\$=`\$
 
-% Misc from plain
+% Misc, mostly from plain
 \let\bgroup={
 \let\egroup=}
 \let\endgraf=\par
 \let\endline=\cr
 \def\empty{}
 \def\space{ }
+\def\tab{^^I}
 \def\null{\hbox{}}
 \def\m@th{\mathsurround=0pt }
 
@@ -67,14 +68,24 @@
 \def\^^M{\ } % control <return> = control <space>
 \def\^^I{\ } % control <tab> = control <space>
 {
-	\catcode`\^^M=13 % these lines must end with %
+	\catcode`\^^M=13 % These lines must end with %.
 	% In \obeylines, we say `\let^^M=\par' instead of `\def^^M{\par}'
-	% since this allows, for example, `\let\par=\cr \obeylines \halign{...'
+	% since this allows, for example, `\let\par=\cr \obeylines \halign{...'.
 	\gdef\obeylines{\catcode`\^^M=13 \let^^M=\par}%
-	\glet^^M=\par % in case ^^M appears in a \write
+	\glet^^M=\par % See The TeXBook, page 254.
 }
 \def\obeyspaces{\catcode`\ =13 }
-{\obeyspaces\glet =\space}
+{\obeyspaces\glet =\space} % See The TeXBook, page 254.
+\def\obeytabs{\catcode`\^^I=13 }
+{\obeytabs\glet^^I=\tab} % See The TeXBook, page 254.
+{
+\obeytabs % These lines can not have tab indents.
+\gdef\@expandtabs{%
+\loop\ifnum\countA>0 \toksA\ea{\the\toksA\ }\decr\countA\repeat
+\obeytabs \edef^^I{\the\toksA}%
+}
+\gdef\expandtabs{\afterassignment\@expandtabs \countA=}
+}
 
 % Mode control
 \def\leavevmode{\unhbox\voidbox} \def\hmode{\leavevmode}