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%  Copyright (c) 1998 Matijs van Zuijlen
% 
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%\iffalse    This is a METACOMMENT
%
%% Package `synttree' to use with LaTeX 2e
%% Copyright (C) 1998 by Matijs van Zuijlen
%
% Version:     Date:     Changes:
% 1.0        1998/07/19  First version as a .dtx distibution.
%
%\fi
%\MakeShortVerb{\"} 
% \title{The "synttree" package for typesetting syntactic
% trees.\footnote{Package version 0.9, documentation version 0.1}}
% \author{Matijs van Zuijlen}
%
% \maketitle
%
% \begin{abstract}
%   The "synttree" package provides a simple way to typeset syntactic
%   trees as used in Chomsky's Generative Grammar.
% \end{abstract}
%
% {\parskip 0pt                ^^A We have to reset \parskip
%                              ^^A (bug in \LaTeX)
% \tableofcontents
% }
%  \section{Introduction}
%
%  The "synttree" package provides a macro for creating syntactic tree
%  structures such as those used in Noam Chomsky's Generative Grammar.
%  It is designed to create a tree that looks nice, with as little use
%  of `special effects', such as PostScript, as possible.
%
%  In fact, the
%  current implementation uses emTeX "\special"'s, but it should not
%  be hard to use \LaTeXe{}'s spline macro's instead, although this is
%  probably not very nice.
%
%  Since the
%  application is very specific, there is no need for a very complex
%  drawing algorithm. A more complex package is the TreeTeX system
%  \cite{TreeTeX}. This system, however, produces nodes consisting of
%  a node symbol \emph{and} a label, whereas in syntactic trees the
%  label \emph{is} the node symbol. Additionally, the method of
%  specifying the tree structure itself makes the source code hard to
%  read.
%  \iffalse This text is to be ignored.
%
%  The two packages that I have considered using failed on one of
%  these two demands.  First, the "qtree" package did not keep the
%  distance between levels constant. Second, the "???" package used
%  PostScript for output.
%
%  \fi
%
%  Please send any comments or wishes to me, "mzuijlen@integral.nl".
%
%  \section{Usage}
%
%  The single macro that is currently defined by this package is the
%  "\synttree" macro. It takes as arguments first an optional
%  parameter indicating the maximum level of the tree, and second a
%  parameter describing the structure of the tree. Levels are
%  surrounded by "[" and "]".
%
%  Within a level, first, parameters may be added. These are specified
%  by appending a "." to the opening bracket, and appending letters
%  that modify the appearance of the next level. Append a "t" to
%  create a triangle instead of a line going from the label to the
%  level above it, and a "b" to specify that the node has to appear at
%  the bottom of the tree, on a line with the outermost branches. To
%  use "b", a maximum tree depth has to be specified.
%
%  Then, the label: the label has to be separated from the brackets by
%  spaces. After the label, the node's children follow. The are of
%  course surrounde by brackets. They must not be separated from
%  each other or the level's ending bracket by spaces. The only spaces
%  that are allowed are the ones surrounding the words of the labels.
%  No words may appear between the children.
%
%  \subsection{Examples}
%
%  As a simple example, the line
%\begin{verbatim}
%  \synttree[ A [ B ][ C ]]
%\end{verbatim}
%  creates the following tree:
% \begin{trivlist}
%  \item \synttree[ A [ B ][ C ]]
% \end{trivlist}
%
% Using the optional parameters, we may specify
%\begin{verbatim}
%  \synttree{4}[ A [ B [.b C ]][ D [ E ][ F [.t G ]]]]
%\end{verbatim}%
%  to create:
% \begin{trivlist}
%  \item \synttree{4}[ A [ B [.b C ]][ D [ E ][ F [.t G ]]]]
% \end{trivlist}
%
%  \subsection{Wish List}
%
% I hope to add the following features sooner or later:
% \begin{itemize}
%   \item Unlimited number of children. The current limit is two.
%   \item Control over various parameters affecting the `look' of the
%   tree, such as distance between levels.
%   \item The possibility of `sinking' the tree on the current line,
%   so that the top label aligns with the other text, instead of the
%   bottom label.
%   \item The possibility of creating trees within trees.
%   \item The option of not using "\special"'s.
% \end{itemize}
%
%  \StopEventually{
%  \begin{thebibliography}{1}
%  \bibitem{TreeTeX} A. Br{\"u}ggemann-Klein and D. Wood.
%  \newblock {\it Drawing trees nicely with \TeX{}}
%  \newblock {File \texttt{tree\_doc.tex}}
%  \end{thebibliography}
%  }
%
%  \section{Implementation}
%
%  First, the driver bit for creating the documentation.
%    \begin{macrocode}
%<*driver>
\documentclass[a4paper]{ltxdoc}
\usepackage{synttree}
\EnableCrossrefs         
 %\DisableCrossrefs     % Say \DisableCrossrefs if index is ready
\CodelineIndex
\RecordChanges          % Gather update information
 %\OnlyDescription      % comment out for implementation details
 \OldMakeindex         % use if your MakeIndex is pre-v2.9
\setlength\hfuzz{15pt}  % dont make so many
\hbadness=7000          % over and under full box warnings
\begin{document}
   \DocInput{synttree.dtx}
\end{document}
%</driver>
%    \end{macrocode}
%
% \subsection{Drawing specials}
%
% These command are used to draw the lines between the nodes. This is
% an adaptation of the unsupported "eepic" package, and uses specials.
%
%    \begin{macrocode}
\newcount\MTr@tempcnta
\newcount\MTr@tempcntb
%    \end{macrocode}
% "\MTr@linewidth" stores the width of a line, using correct units for
% the specials.
%    \begin{macrocode}
\newcount\MTr@linewidth
\MTr@linewidth\@wholewidth \divide\MTr@linewidth 4736
%    \end{macrocode}
% The line drawing macro itself. Simply draws a line between the two
% points given. Arguments are counters.
%    \begin{macrocode}
\def\MTr@drawline(#1,#2)(#3,#4){%
  \MTr@linewidthspecial%
  \MTr@tempcnta=#1\relax
  \advance \MTr@tempcnta 2368 \divide \MTr@tempcnta 4736
  \MTr@tempcntb=-#2\relax
  \advance \MTr@tempcntb -2368 \divide \MTr@tempcntb 4736
  \MTr@linespecial{\the\MTr@tempcnta}{\the\MTr@tempcntb}%
  \MTr@tempcnta=#3\relax
  \advance \MTr@tempcnta 2368 \divide \MTr@tempcnta 4736
  \MTr@tempcntb=-#4\relax
  \advance \MTr@tempcntb -2368 \divide \MTr@tempcntb 4736
  \MTr@linespecial{\the\MTr@tempcnta}{\the\MTr@tempcntb}%
  \special{fp}%
  \ignorespaces
}
%    \end{macrocode}
% Insert the actual special command for setting the line width:
%    \begin{macrocode}
\def\MTr@linewidthspecial{%
  \special{pn \the\MTr@linewidth}%
}
%    \end{macrocode}
% Insert the actual special command for line drawing.
%    \begin{macrocode}
\def\MTr@linespecial#1#2{%
  \special{pa #1 #2}%
}
%    \end{macrocode}
%
%   \subsection{Definitions}
%
%  Some counters etc.\ are defined.
%
%    \begin{macrocode}
\newcount\MTr@level
\newcount\MTr@maxdepth
\newcount\MTr@numchildren
\newcount\MTr@mybranchmult
\newif\ifMTr@mytriangle
\newsavebox{\MTr@labelbox}
\newsavebox{\MTr@childbox}
%    \end{macrocode}
% Store info for child number one.
%    \begin{macrocode}
\newsavebox{\MTr@childonebox}
\newcount\MTr@childonex
\newcount\MTr@childoney
\newcount\MTr@childonew
\newcount\MTr@childoneheight
\newcount\MTr@childonedepth
\newcount\MTr@childonebranchmult
\newif\ifMTr@childonetriangle
%    \end{macrocode}
% Store info for child number two.
%    \begin{macrocode}
\newsavebox{\MTr@childtwobox}
\newcount\MTr@childtwox
\newcount\MTr@childtwoy
\newcount\MTr@childtwow
\newcount\MTr@childtwoheight
\newcount\MTr@childtwodepth
\newcount\MTr@childtwobranchmult
\newif\ifMTr@childtwotriangle
%
\newcount\MTr@treex
\newcount\MTr@treew
\newcount\MTr@treedepth
\newcount\MTr@treeheight

\newcount\MTr@labeldepth
\newcount\MTr@labelheight
\newcount\MTr@labelhalfwidth

\newcount\MTr@morex

\newcount\MTr@parenty

\newlength{\MTr@minheight}

\newcount\MTr@branchheight
\newcount\MTr@branchmult

\newif\ifMTr@triangle

\newcount\MTr@lineoffset
%    \end{macrocode}
% How far apart are the left and right sides of two children?
%    \begin{macrocode}
\newcount\MTr@childsidesep
%    \end{macrocode}
% How far apart are two lines?
%    \begin{macrocode}
\newcount\MTr@linesep
%    \end{macrocode}
% How far apart are the attachment points of two children?
%    \begin{macrocode}
\newcount\MTr@childattachsep
\newcount\MTr@picwidth
\newcount\MTr@picheight
\newcount\MTr@piconeheight
\newcount\MTr@pictwoheight
\newlength{\MTr@templength}
%    \end{macrocode}
%
% \subsection{Main macro}
% \begin{macro}{\synttree}
% "\synttree" is the main macro.
%    \begin{macrocode}
\def\synttree{%
%    \end{macrocode}
% Adjust some values to my needs: Distance between levels.
%    \begin{macrocode}
  \setlength{\MTr@templength}{0.5in}%
  \MTr@branchheight\MTr@templength%
%    \end{macrocode}
% Distance between the labels and the lines.
%    \begin{macrocode}
  \setlength{\MTr@templength}{2pt}%
  \MTr@lineoffset\MTr@templength%
%    \end{macrocode}
% Minimum label height.
%    \begin{macrocode}
  \setlength{\MTr@minheight}{8pt}%
%    \end{macrocode}
% Minimum seperation between edges of children.
%    \begin{macrocode}
  \settowidth{\MTr@templength}{ }%
  \MTr@childsidesep\MTr@templength%
%    \end{macrocode}
% Minimum separation between attechment of lines to child labels.
%    \begin{macrocode}
  \MTr@childattachsep\MTr@branchheight%
  \MTr@linesep 0%
%    \end{macrocode}
% Measure "picture" coordinates in minimal units.
%    \begin{macrocode}
  \unitlength 1sp%
%    \end{macrocode}
% If the user has not provided a maximum depth, set it to 0. There
% will be no messages concerning depth, except when the bottomlevel
% modifier is used.
%    \begin{macrocode}
  \@ifnextchar[{\MTr@synt@tree{0}}{\MTr@synt@tree}%
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\MTr@synt@tree}
% Now, the real work starts. This macro is called only at the
% beginning of the tree, because we do not have to store the previous
% part in an "lrbox". This macro gobbles one "[", sets maximum depth
% and current level, then starts the scanning process in.
%    \begin{macrocode}
\def\MTr@synt@tree#1[{%
  \MTr@maxdepth#1%
  \MTr@level0%
  \bgroup%
  \MTr@startlevel%
}
%    \end{macrocode}
% \end{macro}
%
% \subsection{Scanning}
% 
% The scanning process is as follows: Suppose we just started at level
% $n$. An "lrbox" has been opened to save the label. As long as we
% encounter items to go into the label, we keep scanning. Then, we
% encounter a "[". The label's "lrbox" is closed, saving the label.
% Then, an "lrbox" is opened to hold the first child, and level $n+1$
% is opened, starting another label "lrbox" to hold the label for this
% new level. After scanning the label, we encounter a "]". The child's
% label is saved, and the child itself is typeset. For reasons that
% will become clear in a moment, the child itself is not saved yet.
% Next, we may encounter a "[" or a "]".
% If we find a "[", we save the child, start a child "lrbox", and
% go to level $n+1$ again, and start a label "lrbox". Suppose the
% second child also has no children. Upon leaving the
% child, we save the label, and typeset the child. Then, back at level
% $n$, we find another "]". This causes the second child to be saved,
% and level $n$ to be typeset, landing us at level $n-1$. If this is
% the starting level, we now have typeset the whole tree. Otherwise,
% a "[" or "]" will cause this level to be stored in an "lrbox" as
% well.
%
% Thus, we see the following thing happening: a "[" closes an "lrbox",
% then opens two; a "]" closes one "lrbox".
%
% There is one exception to this rule: At the start of the tree, the
% "[" opens just one "lrbox".
% This means, that the final "]" may not close two "lrbox"es: It would
% then close one "lrbox" too many. Instead, the "]" simply signals the
% creation of the outermost level, which is typeset directly since it
% is not being stored in an lrbox. Because no "]" or "[" follows it,
% no more scanning takes place, and the tree is finished.
%
% \begin{macro}{\MTr@scan}
% Generic scan function, used in the definition of "\MTr@scanin" and
% "\MTr@scanout".
%    \begin{macrocode}
\def\MTr@scan{%
    \@ifnextchar[{%
        \MTr@savelabelorchild%
        \MTr@goin}{%
    \@ifnextchar]{%
        \MTr@savelabelorchild%
        \MTr@goout}{%
    \relax\MTr@maybegrabtoken}}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\MTr@scanin}
% Scan upon entering a level: Use "\MTr@grabtoken" to scan the label.
%    \begin{macrocode}
\def\MTr@scanin{\let\MTr@maybegrabtoken\MTr@grabtoken\MTr@scan}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\Mtr@scanout}
% Scan after we already had one or more children: Just ignore anything
% that is not a "[" or "]".
%    \begin{macrocode}
\def\MTr@scanout{\let\MTr@maybegrabtoken\relax\MTr@scan}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\MTr@grabtoken}
% While we are processing tokens for storage, we know that
% "\MTr@maybegrabtoken", used in "\MTr@scan", will be equal to
% "\MTr@grabtoken".
%    \begin{macrocode}
\def\MTr@grabtoken#1 {%
    {#1 }%
    \relax\MTr@scan}
%    \end{macrocode}
% \end{macro}
%
% \subsection{Going In}
%
% \begin{macro}{\MTr@goin}
% Eat the "[" here, start a child box, start a group so everything
% inside the child is local again, and start the child.
%    \begin{macrocode}
\def\MTr@goin[{%
  \advance\MTr@numchildren 1%
  \begin{lrbox}{\MTr@childbox}%
  \bgroup%
  \MTr@startlevel}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\MTr@startlevel}
% In a whole new world now: We begin (again) by setting the number of
% children to 0, and then reading any parameters for this level.
%    \begin{macrocode}
\def\MTr@startlevel{%
  \MTr@numchildren 0%
  \global\advance\MTr@level 1%
  \@ifnextchar.{%
    \MTr@setparameters%
  }{%
    \MTr@setparameters.n %
  }}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\MTr@setparameters}
% Set the parameters for this level, then start scanning the label.
%    \begin{macrocode}
\def\MTr@setparameters.#1 {%
  \MTr@bottomnodefalse%
  \MTr@mytrianglefalse%
  \ifx#1b\MTr@bottomnodetrue\else%
  \ifx#1{bt}\MTr@bottomnodetrue\MTr@mytriangletrue\else%
  \ifx#1{tb}\MTr@bottomnodetrue\MTr@mytriangletrue\else%
  \ifx#1t\MTr@mytriangletrue\else%
  \ifx#1n\relax\else%
  \typeout{MyTree Warning: unknown option #1 in tree}%
  \fi\fi\fi\fi\fi%
  \begin{lrbox}{\MTr@labelbox}%
  \MTr@scanin}
%    \end{macrocode}
% \end{macro}
%
% \subsection{Bottom Nodes}
% 
% For bottom nodes, we have to adapt the vertical position so that
% they become, indeed, bottom nodes. This is done by the macros
% "\MTr@bottomnodetrue" and "\MTr@bottomnodefalse".
%
% \begin{macro}{\MTr@bottomnodetrue}
% The node is a bottom node. Calculate the difference between this
% level and the bottom level as passed to "\synttree", and use this to
% determine how many levels the node has to be advanced vertically to
% get it at the correct position. In effect, the distance between two
% levels is multiplied by the ``branch multiplication.'' For
% non-bottom nodes this is set to 1.
%    \begin{macrocode}
\def\MTr@bottomnodetrue{%
  \MTr@branchmult\MTr@maxdepth%
  \advance\MTr@branchmult-\MTr@level%
  \advance\MTr@branchmult 1%
  \ifnum\MTr@branchmult<0%
    \typeout{XTree Warning: Tree has more levels than indicated.}%
    \typeout{>> Indicated: \the\MTr@maxdepth.}%
    \typeout{>> Level now: \the\MTr@level.}%
    \typeout{>> Mult now: \the\MTr@branchmult.}%
    \MTr@branchmult1%
  \fi%
  \MTr@mybranchmult\MTr@branchmult}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\MTr@bottomnodefalse}
% It's not a bottom node: Just set the branch multiplication to 1.
%    \begin{macrocode}
\def\MTr@bottomnodefalse{%
  \MTr@mybranchmult1}
%    \end{macrocode}
% \end{macro}
%
% \subsection{Going Out}
% \begin{macro}{\MTr@goout}
% We are at the end of the level. The scan function already saved
% everything, so now , we have to make the actual tree for this level.
%
%    \begin{macrocode}
\def\MTr@goout]{%
  \MTr@maketree%
%    \end{macrocode}
% Pass branch multiplication and status of being a triangle on to
% higher level. This level will store these values for the child in
% question.
%    \begin{macrocode}
  \global\MTr@branchmult\MTr@mybranchmult%
  \ifMTr@mytriangle%
    \global\MTr@triangletrue%
  \else%
    \global\MTr@trianglefalse%
  \fi%
%    \end{macrocode}
% Actually end the child, then start scanning again.
%    \begin{macrocode}
  \egroup%
  \global\advance\MTr@level -1%
  \MTr@scanout}
%    \end{macrocode}
% \end{macro}
%
% \subsection{Saving the children}
% Here are the macros for actually storing the children in the child
% boxes. For each child, store the tree itself, its $x$ position, its
% width, height and depth, its branch multiplication and whether or
% not it is a triangle.
%    \begin{macrocode}
\def\MTr@saveone{%
  \sbox{\MTr@childonebox}{\usebox{\MTr@childbox}}%
  \MTr@childonex\MTr@treex%
  \MTr@childonew\MTr@treew%
  \MTr@childoneheight\MTr@treeheight%
  \MTr@childonedepth\MTr@treedepth%
  \MTr@childonebranchmult\MTr@branchmult%
  \ifMTr@triangle%
    \MTr@childonetriangletrue%
  \else%
    \MTr@childonetrianglefalse%
  \fi}
%    \end{macrocode}
% Save child number two.
%    \begin{macrocode}
\def\MTr@savetwo{%
  \sbox{\MTr@childtwobox}{\usebox{\MTr@childbox}}%
  \MTr@childtwox\MTr@treex%
  \MTr@childtwow\MTr@treew%
  \MTr@childtwoheight\MTr@treeheight%
  \MTr@childtwodepth\MTr@treedepth%
  \MTr@childtwobranchmult\MTr@branchmult%
  \ifMTr@triangle%
    \MTr@childtwotriangletrue%
  \else%
    \MTr@childtwotrianglefalse%
  \fi}
%    \end{macrocode}
% Save any child.
%    \begin{macrocode}
\def\MTr@savelabelorchild{%
  \end{lrbox}%
  \ifnum\MTr@numchildren=0
    \relax%
  \else
    \ifnum\MTr@numchildren=1
      \MTr@saveone%
    \else
      \ifnum\MTr@numchildren=2
        \MTr@savetwo%
      \else
        \typeout{MyTree Error: Trying to save third child.}%
      \fi
    \fi
  \fi
}
%    \end{macrocode}
% \subsection{Creating the tree}
% \begin{macro}{\MTr@maketree}
% This macro is a horrible beast. It is the complete code for making
% the actual tree. It has completely separate implementations for each
% number of children from zero to two. It is my intention to modify
% this to allow any number of children to be displayed.
%    \begin{macrocode}
\def\MTr@maketree{%
  \MTr@labelheight\ht\MTr@labelbox%
  \ifnum\MTr@labelheight<\MTr@minheight\MTr@labelheight\MTr@minheight\fi%%
  \MTr@labeldepth\dp\MTr@labelbox%
  \MTr@labelhalfwidth\wd\MTr@labelbox%
  \divide\MTr@labelhalfwidth 2%
  \ifnum\MTr@numchildren=0%
    \MTr@outputlabel%
  \fi%%
  \ifnum\MTr@numchildren=1%
    \MTr@outputonechild%
  \fi%%
%    \end{macrocode}
% Two children
%    \begin{macrocode}
  \ifnum\MTr@numchildren>1%
    \MTr@outputtwochildren%
  \fi%%
  \ifnum\MTr@numchildren>2%
    \relax%
  \fi%%
}%
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\MTr@outputlabel}
% Output just the label.
%    \begin{macrocode}
\def\MTr@outputlabel{%
%    \end{macrocode}
% First, set parameters: Height and depth of
% the subtree are equal to height and depth of the label. The $x$ and
% $w$ of the subtree each equal half the width of the label.
% Optionally, $x$ may be zero and $w$ may equal the entire width of
% the label. The width and height of the picture to be drawn equal the
% width of the label and the heaght of the tree.
%    \begin{macrocode}
    \global\MTr@treeheight\MTr@labelheight%
    \global\MTr@treedepth\MTr@labeldepth%
    \ifMTr@mytriangle%
%%      \global\MTr@treew\wd\MTr@labelbox%
%%      \global\MTr@treex0%
      \global\MTr@treew\MTr@labelhalfwidth%
      \global\MTr@treex\MTr@labelhalfwidth%
    \else%
      \global\MTr@treew\MTr@labelhalfwidth%
      \global\MTr@treex\MTr@labelhalfwidth%
    \fi%
    \MTr@picwidth\wd\MTr@labelbox%
    \MTr@picheight\MTr@treeheight%
%    \end{macrocode}
% Second, draw the picture. The coordinates for the picture are nearly
% the same throughout. In any event, the label is centered in the
% picture, its baseline aligned with the bottom of the picture.
%    \begin{macrocode}
    \advance\MTr@picheight\MTr@treedepth%
    \begin{picture}%
        (\MTr@picwidth,\MTr@picheight)%
        (-\MTr@treex,-\MTr@picheight)%
      \put(-\MTr@treex,0){%
        \makebox(0,0)[tl]{%
          \rule{0pt}{\MTr@minheight}%
          \usebox{\MTr@labelbox}}}%
    \end{picture}%
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\MTr@outputonechild}
% Output label and one child.
%    \begin{macrocode}
\def\MTr@outputonechild{%
    \MTr@treex\MTr@childonex%
    \MTr@treew\MTr@childonew%
    \MTr@morex\MTr@labelhalfwidth%
    \advance\MTr@morex -\MTr@treex%
    \ifnum\MTr@morex<0\MTr@morex0\else\MTr@treex\MTr@labelhalfwidth\fi%
    \ifnum\MTr@treew<\MTr@labelhalfwidth\MTr@treew\MTr@labelhalfwidth\fi%
    \MTr@picwidth\MTr@treex\advance\MTr@picwidth\MTr@treew%
    \MTr@childoney-\MTr@branchheight%
    \multiply\MTr@childoney\MTr@childonebranchmult%
    \MTr@picheight-\MTr@childoney%
    \advance\MTr@picheight\MTr@childonedepth%
    \advance\MTr@childoney-\MTr@labelheight%
    \advance\MTr@childoney\MTr@childoneheight%
    \global\MTr@treedepth\MTr@picheight%
    \advance\MTr@picheight\MTr@labelheight%
    \global\MTr@treeheight\MTr@labelheight%
    \MTr@parenty-\MTr@labelheight%
    \advance\MTr@parenty-\MTr@labeldepth%
    \advance\MTr@parenty-\MTr@lineoffset%
    \global\MTr@treex\MTr@treex%
    \global\MTr@treew\MTr@treew%
    \begin{picture}%
          (\MTr@picwidth,\MTr@picheight)%
          (0,-\MTr@picheight)%
      \put(\MTr@treex,0){%
        \makebox(0,0)[t]{%
          \rule{0pt}{\MTr@minheight}%
          \usebox{\MTr@labelbox}}}%
      \put(\MTr@morex,\MTr@childoney){%
        \makebox(0,0)[tl]{%
          \usebox{\MTr@childonebox}}}%
      \advance\MTr@childoney\MTr@lineoffset%
      \ifMTr@childonetriangle%
        \put(\MTr@treex,0){\MTr@drawline%
            (0,\MTr@parenty)%
            (-\MTr@childonex,\MTr@childoney)}%
        \put(\MTr@treex,0){\MTr@drawline%
            (0,\MTr@parenty)%
            (\MTr@childonew,\MTr@childoney)}%
        \put(\MTr@treex,0){\MTr@drawline%
            (-\MTr@childonex,\MTr@childoney)%
            (\MTr@childonew,\MTr@childoney)}%
      \else%
        \put(0,0){\MTr@drawline%
            (\MTr@treex,\MTr@parenty)%
            (\MTr@treex,\MTr@childoney)}%
      \fi%
    \end{picture}%
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\MTr@outputtwochildren}
% Two children.
%    \begin{macrocode}
\def\MTr@outputtwochildren{%
%    \end{macrocode}
% Calculate desired distance between the two children.
%    \begin{macrocode}
    \advance\MTr@childonew\MTr@childsidesep%
    \MTr@treex\MTr@childonew%
    \advance\MTr@treex\MTr@childtwox%
    \ifnum\MTr@treex<\MTr@childattachsep%
      \advance\MTr@childonew\MTr@childattachsep%
      \advance\MTr@childonew-\MTr@treex%
      \MTr@treex\MTr@childattachsep%
    \fi%
%    \end{macrocode}
% Calculate the subtree's $x$ and $w$:
%    \begin{macrocode}
    \divide\MTr@treex 2%
    \MTr@treew\MTr@treex%
    \advance\MTr@treex\MTr@childonex%
    \advance\MTr@treew\MTr@childtwow%
%    \end{macrocode}
% Calculate "morex": The distance the subtree has to be shifted to the
% right to accomodate a large label size.
%    \begin{macrocode}
    \MTr@morex\MTr@labelhalfwidth%
    \advance\MTr@morex-\MTr@treex%
    \ifnum\MTr@morex<0\MTr@morex0\fi%
%    \end{macrocode}
% Large label sizes are immedeately incorporated into $w$.
%    \begin{macrocode}
    \ifnum\MTr@treew<\MTr@labelhalfwidth\MTr@treew\MTr@labelhalfwidth\fi%
%    \end{macrocode}
% Picture width.
%    \begin{macrocode}
    \MTr@picwidth\MTr@treex%
    \advance\MTr@picwidth\MTr@treew%
%    \end{macrocode}
% Something for child one.
%    \begin{macrocode}
    \MTr@childoney-\MTr@branchheight%
    \multiply\MTr@childoney\MTr@childonebranchmult%
    \MTr@piconeheight-\MTr@childoney%
    \advance\MTr@piconeheight\MTr@childonedepth%
    \advance\MTr@childoney-\MTr@labelheight%
    \advance\MTr@childoney\MTr@childoneheight%
%    \end{macrocode}
% Same thing for child two.
%    \begin{macrocode}
    \MTr@childtwoy-\MTr@branchheight%
    \multiply\MTr@childtwoy\MTr@childtwobranchmult%
    \MTr@pictwoheight-\MTr@childtwoy%
    \advance\MTr@pictwoheight\MTr@childtwodepth%
    \advance\MTr@childtwoy-\MTr@labelheight%
    \advance\MTr@childtwoy\MTr@childtwoheight%
%    \end{macrocode}
% Compare height based on child one with that based on child two.
%    \begin{macrocode}
    \ifnum\MTr@piconeheight>\MTr@pictwoheight%
      \MTr@picheight\MTr@piconeheight%
    \else%
      \MTr@picheight\MTr@pictwoheight%
    \fi%
    \global\MTr@treedepth\MTr@picheight%
    \advance\MTr@picheight\MTr@labelheight%
    \global\MTr@treeheight\MTr@labelheight%
    \MTr@parenty-\MTr@labelheight%
    \advance\MTr@parenty-\MTr@labeldepth%
    \advance\MTr@parenty-\MTr@lineoffset%
    \global\MTr@treex\MTr@treex%
    \global\MTr@treew\MTr@treew%
%    \end{macrocode}
% Draw the picture.
%    \begin{macrocode}
    \begin{picture}(\MTr@picwidth,\MTr@picheight)(0,-\MTr@picheight)%
      \put(\MTr@treex,0){%
        \makebox(0,0)[t]{%
          \rule{0pt}{\MTr@minheight}%
          \usebox{\MTr@labelbox}}}%
      \put(\MTr@morex,\MTr@childoney){%
        \makebox(0,0)[tl]{%
          \usebox{\MTr@childonebox}}}%
      \advance\MTr@childonex\MTr@morex%
      \advance\MTr@childoney\MTr@lineoffset%
      \MTr@morex\MTr@childonex%
      \advance\MTr@morex\MTr@childonew%
      \put(\MTr@morex,\MTr@childtwoy){%
        \makebox(0,0)[tl]{%
          \usebox{\MTr@childtwobox}}}%
      \advance\MTr@childtwox\MTr@morex%
      \advance\MTr@childtwoy\MTr@lineoffset%
      \put(0,0){\MTr@drawline%
        (\MTr@treex,\MTr@parenty)%
        (\MTr@childonex,\MTr@childoney)}%
      \put(0,0){\MTr@drawline%
        (\MTr@treex,\MTr@parenty)%
        (\MTr@childtwox,\MTr@childtwoy)}%
    \end{picture}%
}
%    \end{macrocode}
% \end{macro}
%
% \Finale
% \PrintIndex \PrintChanges
\endinput