Is there in plain TeX a macro similar to \leftarrowfill but vertically oriented, something like \uparrowfill? I know it exists in LaTeX, but I'm interested only in plain TeX.

• Can you add some context where you would be using such a macro? – egreg Dec 18 '13 at 18:33
• @egreg Something like \vbox to 5in{\hsize=.5in\vbox to2in{\uparrowfill}\vskip1in\vbox to2in{\downarrowfill}} – Jean Baldraque Dec 18 '13 at 18:43

I don't understand what this should be for, but this could work.

\def\downarrowfill{%
\par
\begingroup\offinterlineskip
\setbox0=\hbox{$\downarrow$}%
\setbox2=\hbox to\wd0{\hss$|$\hss}%
\copy2
\kern-3pt
\kern-3pt
\box0
\endgroup
}
\def\uparrowfill{%
\par
\begingroup\offinterlineskip
\setbox0=\hbox{$\uparrow$}%
\setbox2=\hbox to\wd0{\hss$|$\hss}%
\copy0
\kern-3pt
\kern-3pt
\box2
\endgroup
}

\vbox to 3cm{\hsize=1cm\vbox to1cm{\uparrowfill}\vfill\vbox to1cm{\downarrowfill}}

\bye


An alternative way:

\def\arrowto#1#2{%
\setbox0=\hbox{%
$\left#1% \vcenter to #2{} \right. \kern-\nulldelimiterspace$%
}%
\leavevmode\raise\dp0\box0}
\def\uparrowto{\arrowto\uparrow}
\def\downarrowto{\arrowto\downarrow}

a\uparrowto{12pt}a\downarrowto{12pt}a

\bye


• one use: for drawing rectangular commutative diagrams. – barbara beeton Dec 18 '13 at 20:06
• @egreg you've given a spectacular answer, as usual. – Jean Baldraque Dec 19 '13 at 8:50