% 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 9.3.9.1, p. I-335.
% Original source in file "boxit.TEX", starting line 1131.
\wlog{L: "boxing7.tip" ["boxit.TEX," l. 1131, p. I-335]}%
% This file DOES belong to format "texip."
\InputD{boxing6.tip}
\InputD{vcentx.tip}
\catcode`\@ = 11
\newdimen\@BoxRDimen
\newbox\@BoxRBox
\newcount\@BoxRNumber
\def\HboxR{%
    \hbox\bgroup
    \def\@WhichBox{\hbox}%
    \def\@WhichBoxDimen{}%
    \@BoxRaa
}
\def\VboxR{%
    \vbox\bgroup
    \def\@WhichBox{\vbox}%
    \def\@WhichBoxDimen{}%
    \@BoxRaa
}
\def\VtopR{%
    \vtop\bgroup
    \def\@WhichBox{\vtop}%
    \def\@WhichBoxDimen{}%
    \@BoxRaa
}
\def\VcenterXR{%
    \hbox\bgroup
    \def\@WhichBox{\VcenterX}%
    \def\@WhichBoxDimen{}%
    \@BoxRaa
}
\def\BoxR{%
    \hbox\bgroup
    \def\@WhichBox{\hbox}%
    \def\@WhichBoxDimen{}%
    \afterassignment\@BoxRB
    \@BoxRNumber =
}
\def\@BoxRB{%
    \HboxR{\box\@BoxRNumber}% 
    \egroup
}
\def\CopyR{%
    \hbox\bgroup
    \def\@WhichBox{\hbox}%
    \def\@WhichBoxDimen{}%
    \afterassignment\@CopyRbb
    \@BoxRNumber =
}
\def\@CopyRbb{%
    \HboxR{\copy\@BoxRNumber}% 
    \egroup
}
\def\@BoxRaa{% 
    \futurelet\@BoxRSymbol\@BoxRA
}
\def\@BoxRA{%
    \ifx\@BoxRSymbol\bgroup
        \let\@BoxitNext = \@BoxRb
    \else
        \if\@BoxRSymbol t% 
            \let\@BoxitNext = \@BoxRbTo
        \else
            \let\@BoxitNext = \@BoxRbSpread
        \fi
    \fi
    \@BoxitNext
}
\def\@BoxRb{%
    \afterassignment\@BoxRbTwo
    \let\@BoxDrop =
}
\def\@BoxRbTwo{% 
    \setbox\@BoxRBox = \expandafter\@WhichBox\@WhichBoxDimen\bgroup
    \aftergroup\@BoxRbThree
}
\def\@BoxRbThree{% 
    \BoxingE{\box\@BoxRBox}% 
    \egroup
}
\def\@BoxRbTo to{%
    \def\@WhichBoxDimen{to}% 
    \afterassignment\@BoxRbMoreSpreadTo
    \@BoxRDimen =
}
\def\@BoxRbSpread spread{%
    \def\@WhichBoxDimen{spread}%
    \afterassignment\@BoxRbMoreSpreadTo
    \@BoxRDimen =
}
\def\@BoxRbMoreSpreadTo{%
    \edef\@WhichBoxDimen{\@WhichBoxDimen \the\@BoxRDimen}% 
    \afterassignment\@BoxRbTwo
    \let\@BoxDrop =
}
\catcode`\@ = 12