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+%  longdiv.tex  v.1  (1994)  Donald Arseneau  
+%
+%  Work out and print integer long division problems.  Use:
+%       \longdiv{numerator}{denominator}
+%  The numerator and denominator (divisor and dividend) must be integers, and
+%  the quotient is an integer too.  \longdiv leaves a remainder.
+%  Use this in any type of TeX.
+
+\newcount\gpten % (global) power-of-ten -- tells which digit we are doing
+\countdef\rtot2 % running total -- remainder so far
+\countdef\LDscratch4 % scratch
+
+\def\longdiv#1#2{%
+ \vtop{\normalbaselines \offinterlineskip
+   \setbox\strutbox\hbox{\vrule height 2.1ex depth .5ex width0ex}%
+   \def\showdig{$\underline{\the\LDscratch\strut}$\cr\the\rtot\strut\cr
+       \noalign{\kern-.2ex}}%
+   \global\rtot=#1\relax
+   \count0=\rtot\divide\count0by#2\edef\quotient{\the\count0}%\show\quotient
+   % make list macro out of digits in quotient:
+   \def\temp##1{\ifx##1\temp\else \noexpand\dodig ##1\expandafter\temp\fi}%
+   \edef\routine{\expandafter\temp\quotient\temp}%
+   % process list to give power-of-ten:
+   \def\dodig##1{\global\multiply\gpten by10 }\global\gpten=1 \routine
+   % to display effect of one digit in quotient (zero ignored):
+   \def\dodig##1{\global\divide\gpten by10
+      \LDscratch =\gpten
+      \multiply\LDscratch  by##1%
+      \multiply\LDscratch  by#2%
+      \global\advance\rtot-\LDscratch \relax
+      \ifnum\LDscratch>0 \showdig \fi % must hide \cr in a macro to skip it
+   }%
+   \tabskip=0pt
+   \halign{\hfil##\cr % \halign for entire division problem
+     $\quotient$\strut\cr
+     #2$\,\overline{\vphantom{\big)}%
+     \hbox{\smash{\raise3.5\fontdimen8\textfont3\hbox{$\big)$}}}%
+     \mkern2mu \the\rtot}$\cr\noalign{\kern-.2ex}
+     \routine \cr % do each digit in quotient
+}}}
+
+\endinput % Demonstration below:
+
+\noindent Here are some long division problems
+
+\indent
+\longdiv{12345}{13} \quad
+\longdiv{123}{1234} \quad
+\longdiv{31415926}{2} \quad
+\longdiv{81}{3} \quad
+\longdiv{1132}{99} \quad
+\longdiv{86491}{94}
+\bye