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+% This macro source file is from the four volume series
+% "TeX in Practice" by Stephan von Bechtolsheim, published
+% 1993 by Springer-Verlag, New York.
+% Copyright 1993 Stephan von Bechtolsheim.
+% No warranty or liability is assumed.
+% This macro may be copied freely if no fees other than
+% media cost or shipping charges are charged and as long
+% as this copyright and the following source code itself
+% is not changed. Please see the series for further information.
+%
+% Version: 1.0
+% Date: May 1, 1993
+%
+%
+% This source code is documented in 27.1.8, p. III-412.
+% Original source in file "macros7.TEX", starting line 768.
+\wlog{L: "doloop.tip" ["macros7.TEX," l. 768, p. III-412]}%
+% This file DOES belong to format "texip."
+\catcode`\@ = 11
+\newcount\@DoLoopNesting
+\@DoLoopNesting = 0
+\newcount\@DoLoopLimit
+\newcount\@DoLoopLimitTwo
+\newcount\@DoLoopLimitThree
+\def\DoLoop #1#2#3#4#5{%
+ \global\advance\@DoLoopNesting by 1
+ \ifnum\@DoLoopNesting > 3
+ \errmessage{\string\DoLoop: nesting beyond three levels
+ is not supported.}%
+ \fi
+ \ifnum #3 = 0
+ \errmessage{\string\DoLoop: step value (parameter 3) is 0!}%
+ \else
+ \ifcase\@DoLoopNesting
+ \or
+ \@DoLoop{#1}{#2}{#3}{#4}{#5}%
+ {\@DoLoopLimit}{\DoLoopBody}%
+ \or
+ \@DoLoop{#1}{#2}{#3}{#4}{#5}%
+ {\@DoLoopLimitTwo}{\DoLoopBodyTwo}%
+ \or
+ \@DoLoop{#1}{#2}{#3}{#4}{#5}%
+ {\@DoLoopLimitThree}{\DoLoopBodyThree}%
+ \fi
+ \fi
+ \global\advance\@DoLoopNesting by -1
+}
+\def\@DoLoop #1#2#3#4#5#6#7{%
+ \ifnum #3 > 0
+ #6 = #4%
+ \advance#6 by 1
+ #1 = #2%
+ \@DoLoopBodyPositive{#1}{#3}{#5}%
+ {#6}{#7}%
+ \else
+ #6 = #4%
+ \advance#6 by -1
+ #1 = #2%
+ \@DoLoopBodyNegative{#1}{#3}{#5}%
+ {#6}{#7}%
+ \fi
+ \@DoLoopIterate{#7}%
+}
+\def\@DoLoopBodyPositive #1#2#3#4#5{%
+ \def #5{%
+ \ifnum #1 < #4\relax
+ #3%
+ \advance #1 by #2%
+ }%
+}
+\def\@DoLoopBodyNegative #1#2#3#4#5{%
+ \def #5{%
+ \ifnum #1 > #4\relax
+ #3%
+ \advance #1 by #2%
+ }%
+}
+\def\@DoLoopIterate #1{%
+ #1\relax
+ \def\@DoLoopNext{\@DoLoopIterate{#1}}%
+ \else
+ \def\@DoLoopNext{\relax}%
+ \fi
+ \@DoLoopNext
+}
+\catcode`\@ = 12