cmp_tree.tex

%%-*-latex-*-

\documentclass[11pt]{article}

\usepackage{pst-tree,pst-eps}

\begin{document}

\TeXtoEPS
%\psset{showbbox=true}
\pstree[nodesep=2pt,levelsep=24pt,treesep=7pt]{\TR{\(a_1\)?\(a_2\)}}{
  \psset{tpos=0.2,levelsep=24pt}
  \pstree{\TR{\(a_2\)?\(a_3\)}\tlput{\(_{<}\)}}{
    \psset{tpos=0.3}
    \TR{\((a_1,a_2,a_3)\)} \tlput{\(_{<}\!\!\)}
    \pstree{\TR{\(a_1\)?\(a_3\)}\trput{\(\!\!_{>}\)}}{
      \TR{\((a_1,a_3,a_2)\)}\tlput{\(_{<}\!\!\)}
      \TR{\((a_3,a_1,a_2)\)}\trput{\(\!\!_{>}\)}
    }
  }
  \pstree{\TR{\(a_2\)?\(a_3\)}\trput{\(_{>}\)}}{
    \psset{tpos=0.3}
    \pstree{\TR{\(a_1\)?\(a_3\)}\tlput{\(_{<}\!\!\)}}{
      \TR{\((a_2,a_1,a_3)\)}\tlput{\(_{<}\!\!\)}
      \TR{\((a_2,a_3,a_1)\)}\trput{\(\!\!_{>}\)}
    }
    \TR{\((a_3,a_2,a_1)\)}\trput{\(\!\!_{>}\)}
  }
}
\endTeXtoEPS

\end{document}