plain-texrules
I have looked at this question as well as here and here but I cannot figure out how to produce a long underscore in plain TeX, as in the following example.
Date _____________________________
The closest I have come is the obviously undesirable concatenation which leaves gaps in the rendered output.
Date \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Try the file below. You asked for Plain TeX - so this must be run with pdftex (not pdflatex). This file (vert.tex) and some test files are hosted on GitHub at https://github.com/m4dc4p/vert.
%% Justin Bailey 2011
%% jgbailey@codeslower.com
%%
%% To use: surround paragraphs to place a rule
%% with \startrule and \endrule.
%%
%% E.g.:
%%
%% \startrule
%% This paragraph will have a rule around it.
%% \endrule
%%
%% Multiple paragraphs can be spanned as well. Rules will break across
%% pages. Unfortunately, glue between paragraphs will not stretch
%% in that case, but usually it's not noticeable.
%%
%% You can change the offset of the rule by setting \ruleoffset. Rules
%% are always offset from the left margin.
%%
%% A simple \codeblock environment is included too.
%%
%% To use it, surround the code with \codeblock{
%%
%% }
%%
%% Code must appear in the group. The group must immediately follow \codeblock.
%% Code is set ragged right, obeying newlines, using typewriter font.
\newdimen\ruleoffset \ruleoffset=-10pt %% Horizontal offset for the
%% rule. This is the parameter that
%% should be set by the user.
\newdimen\roffset %% For calculating offset from left margin for rule.
\newbox\savedbox \newif\ifoutputran \newbox\rulebox
\newdimen\splitheight \newdimen\interparskip
\newtoks\codetoks
%% The basic idea is to use TeX's output routines
%% to determine if our ruled box is too high. If so
%% we split the box, set a rule, and put the rest on
%% the next page. \endrule does most of the work.
\def\startrule{%%
%% Clear our saved box.
\setbox0=\hbox{\box\savedbox}\par%%
%% Save \ruleoffset for later use.
\xdef\setroffset{\roffset=\the\leftskip \advance\roffset by \the\ruleoffset}%%
%% Save \prevdepth so we can use it to calculate interparagraph
%% glue.
\xdef\theprevdepth{\the\prevdepth}%%
%% Save material proceeding \startrule unless we're at
%% the top of the page.
\output={\accum}\ifnum\pagegoal<\maxdimen\relax%%
\vfil\break\outputranfalse%%
%% Capture everything up to \endrule in a \vbox.
\fi\setbox\rulebox=\vbox\bgroup}
\def\endrule{\egroup%%
%% Test if \rulebox + \savedbox will overflow
%% the page.
\output{\test}%%
\setinterparskip\setroffset%%
\setbox4=\makerule\copy\rulebox/%%
%% \vfuzz and \vbadness set to avoid overfull/underfull warnings
%% while testing.
\edef\thevfuzz{\the\vfuzz}\edef\thevbadness{\the\vbadness}%%
\vfuzz=10in\box4\penalty0%%
%% Restore default output routine.
\output={\savedout}\vfuzz=\thevfuzz%%
\ifoutputran\outputranfalse%%
%% The material overflowed the page, so we split off what
%% can fit (\splitheight) and put that on the page.
\vfuzz=10in\vbadness=10000%%
\setbox0=\vsplit\rulebox to \splitheight\vbadness=\thevbadness%%
\makerule\box0/\break\vfuzz=\thevfuzz%%
%% Put remaining material in a ruled box unless
%% nothing was left (\ifvoid)
\ifvoid\rulebox%%
\else\startrule\unvbox\rulebox\endrule%%
\fi%%
\fi}
%% Ensures spaces at the beginning of the line are always
%% preserved. TABs will not be. Thanks to TeX for the Impatient
%% (eplain) for \alwayspace.
{\gdef\alwaysspace{\hglue\fontdimen2\the\font \relax}%%
\obeyspaces\gdef {\alwaysspace}}
%% Define new lines so that in \codeblock they don't start a new
%% paragraph - they just insert a line break.
{\catcode`\^^M=\active \gdef^^M{\null\hfil\break} \global\let\ret=^^M}
\newtoks\codetoks
%% \codeblock must be followed by a group or it has no effect.
%% When followed by a group, the text found will be set on
%% individual lines as they appear in the group (i.e. new lines
%% are obeyed). The entire group will be have a rule next to it.
%% The group is also set in typewriter font, with ragged-right
%% margins.
%%
%% Note that text in the group is NOT set verbatim.
\def\codeblock{\codetoks={}%%
%% Removes final lineskip if one was there.
\gdef\endo{\unpenalty\endrule\prevdepth=0pt\relax}%%
%% Removes initial newline, if one was there. Otherwise, reinsert the
%% token captured.
\gdef\ignorenewline{\ifx\next\ret%%
\else\next%%
\fi}%%
\gdef\do{\ifx\next\bgroup%%
\codetoks={\startrule\noindent\bgroup%%
\ttraggedright%%
\parindent=0pt%%
\tt%%
\aftergroup\endo%%
\ignorespaces%%
\catcode`\^^M=\active\obeyspaces%%
\afterassignment\ignorenewline\let\next= }%%
\fi\the\codetoks}%%
\ignorespaces\afterassignment\do\let\next= }
\edef\savedout{\the\output}
%% Accumulate vertical material into a box.
\def\accum{\global\setbox\savedbox=\vbox{\unvbox\savedbox\unvbox255\unskip}}
%% An output routine that tells us it ran and
%% throws away the page built.
\def\test{\global\outputrantrue%%
\global\splitheight=\vsize%%
\global\advance\splitheight by -\ht\savedbox%%
\global\advance\splitheight by -\dp\savedbox%%
\setbox0=\vbox{\box255}}
\def\makerule#1/{\vbox{\unvcopy\savedbox%%
\vskip\interparskip\par\penalty0%%
\hbox{\hskip \roffset \vrule \hss \hskip -\roffset \strut#1\strut}}}%%
\def\setinterparskip{\setbox2=\vtop{X\par}%%
\setbox4=\vtop{\unvcopy\rulebox}%%
%% Set \prevdepth so inter-paragraph glue is calculated based
%% on the paragraph that really preceded \startrule, not our
%% fake paragraph.
\setbox0=\vbox{\copy2\par\prevdepth=\theprevdepth\copy4}%%
\interparskip=\ht0 \advance\interparskip by -\ht4 \advance\interparskip by -\ht2}%%
ulemTimebandit had written a solution with package ulem. The example was given as LaTeX, but the package also works with plain TeX:
\input ulem.sty
\sout{Hello World}
\bye
soulAnother LaTeX package soul can be used with plain TeX:
\input soul.sty
\st{Hello World}
\bye
Best Answer
Use a negative height and a slightly bigger depth:
Adjust to suit.
The same idea can be used for “raised rules” (with a negative depth). No rule will appear if depth + height is negative.
If you want a “low rule” that fills up a given space, leaders should be used:
Note that
\leavevmodeis necessary because the command appearing in vertical mode would raise an error because of\hfill(and would do nothing good either).