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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Repeat loop macro, version 0.93, May 2003
% Copyright Victor Eijkhout 2000
% file name: repeat.tex
%
% Author:
% Victor Eijkhout
% Department of Computer Science
% University of Tennessee, Knoxville TN 37996
%
% victor@eijkhout.net
%
% This program is free software; you can redistribute it and/or
% modify it under the terms of the GNU General Public License
% as published by the Free Software Foundation; either version 2
% of the License, or (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% For a copy of the GNU General Public License, write to the
% Free Software Foundation, Inc.,
% 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA,
% or find it on the net, for instance at
% http://www.gnu.org/copyleft/gpl.html
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% General loop macro:
% \repeat
% \for{<var>} \from{<start>} \by{<step>} \to{<end>} \downto{<end>}
% \until{<cond>} \while{<cond>}
% \do { <loop body> }
% where all control sequences in between \repeat and \do are optional.
% The space after each argument is mandatory!
% (This implies that you will have to write "\from\i" as "\from{\i}".)
%
% var: characters to form a control sequence;
% after \for{index} you can access the loop counter as \index.
% This is a count register; to print it use \number\index.
% start,step,end: integers with obvious relations to the loop counter;
% start and step have a default value of 1
% cond: (sequence of commands ending in) any TeX \if... test.
%
% Count down instead of up with \downto; the increment given in \by
% is always positive, and is added or subtracted accordingly.
%
% Tests: \until is evaluated at the end of the loop body; \while
% at the beginning of the loop body.
%
% Exit from middle of loop: \breakrepeat
% use this at any place in the loop; in case of a conditional, use
% \ifsomething ... \expandafter \breakrepeat \fi
%
% There are some examples at the end of this file, after the \endinput line.
%
% Technical details:
% The loop body is not executed in a group: the braces are those
% of a token list.
% The `for' variable is \let to a \count register.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% revision history:
% 0.9 first release, January 1999
% 0.91 documentation update,
% csarg-like control sequences made REP...
% counter update made global in case the body issues grouping,
% copyright notice, February 1999
% 0.92 installed trace switches, eliminated unwanted space caused by
% "\for{ijk} \do{...}", December 2000
% 0.93 added missing percent signs at end of lines to prevent unwanted
% spaces, May 2003 ({\'E}. Dupuis).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%%
%% Prevent multiple loading of this file
%%
\expandafter\ifx\csname REPdepth\endcsname\relax
\message{Loading loop macro, version 0.93}%
\else \endinput \fi
%%
%% Auxiliary stuff
%%
\def\REPcsarg#1#2{\expandafter#1\csname#2\endcsname}
\def\REPcsrom#1{\csname #1\romannumeral\REPdepth\endcsname}
\def\REPcsargrom#1#2{\expandafter#1\csname#2\romannumeral\REPdepth\endcsname}
%\def\cscsarg#1#2#3{\expandafter#1\expandafter#2\csname#3\endcsname}
%\def\REPcsREPcsargrom#1#2#3{\expandafter#1\expandafter#2%
% \csname#3\romannumeral\REPdepth\endcsname}
\newcount\REPdepth
\let\endrepeat\relax \def\csprotect{}
% Trace switches may later be defined by PAC_utils
\let\REPtraceinit\relax \let\REPtraceexit\relax
%%
%% Main repeat macro
%% - go to next level and allocate unique counter/toks if this is the
%% first time we visit this level
%% - setup: gather bounds and termination conditions
%% - scoop up body in token list; after the assignment define and
%% execute body
%%
\def\repeat#1\do{%
\REPtraceinit% exit in \breakrepeat
\advance\REPdepth by 1\relax%
\REPcsargrom\ifx{REPcount}\relax%
\REPcsargrom{\csname newcount\expandafter\endcsname}{REPcount}%
\REPcsargrom{\csname newtoks\expandafter\endcsname}{REPtoks}%
\REPcsargrom{\csname newtoks\expandafter\endcsname}{REPwtest}%
\REPcsargrom{\csname newtoks\expandafter\endcsname}{REPutest}%
\fi \REPzero \def\REPsign{}\def\REPcomp{>}\REPsetup{#1}%
\edef\REPtmp%
{\def\REPcsargrom\noexpand{REPrepeat}{\REPcsargrom\noexpand{REPbody}}}\REPtmp%
\afterassignment\REPdxbody\REPcsrom{REPtoks}}%
%%
%% Define and execute loop body
%% This is done with an \edef to construct the actual sequence
%%
\def\REPdxbody{\REPcsargrom\edef{REPbody}{%
\REPcsargrom\the{REPwtest}%
\noexpand\the\REPcsargrom\noexpand{REPtoks}%
\REPcsargrom\the{REPutest}%
\global\REPcsargrom\advance{REPcount} by \REPsign\REPcsrom{REPinc}\relax%
\noexpand\endrepeat%
\REPcsargrom\noexpand{REPrepeat}}%
\REPcsrom{REPbody}}%
%%
%% Stop test
%% In order to stop, issue a
%% \breakrepeat which scoops up the rest of the body and exits
%%
\def\breakrepeat#1\endrepeat{\REPzero\REPcsargrom\let{REPrepeat}\relax%
\advance\REPdepth by -1 \REPtraceexit%
}%
%%
%% Setup
%% gather bounds and termination conditions
%%
\def\REPsetup#1{%
\begingroup%
\def\for##1 {\edef\REPtmp{%
\global\let\REPcsarg\noexpand{##1}\REPcsrom{REPcount}}\REPtmp}%
\def\from##1 {\REPcsargrom\global{REPcount}##1\relax}%
\def\to##1 {\edef\REPtmp{\global\REPcsargrom\noexpand{REPwtest}=%
{\REPcsargrom\the{REPwtest}%
\noexpand\ifnum\REPcsargrom\noexpand{REPcount}\REPcomp##1\relax%
\noexpand\expandafter \noexpand\breakrepeat \noexpand\fi}}\REPtmp}%
\def\downto##1 {\gdef\REPsign{-}\gdef\REPcomp{<}\to{##1}}%
\def\by##1 {\ifnum##1<0 \message{REPEAT: increment has to be >0}%
\REPcsargrom\gdef{REPinc}{-##1}\else%
\REPcsargrom\gdef{REPinc}{##1}\fi}%
\def\until##1 {\edef\REPtmp{\global\REPcsargrom\noexpand{REPutest}=%
{\noexpand##1\relax%
\noexpand\expandafter \noexpand\breakrepeat \noexpand\fi}}\REPtmp}%
\def\while##1 {\edef\REPtmp{\global\REPcsargrom\noexpand{REPwtest}=%
{\noexpand##1\relax \noexpand\else%
\noexpand\expandafter \noexpand\breakrepeat \noexpand\fi}}\REPtmp}%
\from{1} \by{1} #1%
\endgroup}%
\def\REPzero%
{\REPcsrom{REPtoks}{}\REPcsrom{REPutest}{}\REPcsrom{REPwtest}{}%
\REPcsargrom\def{REPbody}{}}%
\endinput
%\tracingmacros2
\repeat \for{i} \by{2} \do {
\ifnum\i=13 \expandafter\breakrepeat \fi
\message{doing \number\i}
}
\repeat \for{iii} \to{8} \do {}
\message{After loop: \number\iii}
\repeat \for{i} \from{10} \by{2} \downto{0} \do {
\message{countdown \number\i}
}
\repeat \for{x} \while{\ifnum\x<7} \do {
\message{going \number\x}
}
\repeat \to{3} \do {
\message{hello there!}
}
\newcount\tmpcount
\repeat \for{j}
\until{\tmpcount\j \divide\tmpcount by 37 \noexpand\ifnum\tmpcount=1}
\do {
\message{testing \number\j}
}
\repeat \for{i} \by{2} \to{10} \do
{\repeat \for{j} \from{\i} \by{3} \to{18} \do
{\message{(\number\i.\number\j)}
}}
% infinite loop
%\repeat \do {}
\bye
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