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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
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