To accompany http://i.imgur.com/T1l6eN4.png?1

#! /bin/bash

#  I, the copyright holder of this work, hereby release it into the public
#  domain.  This applies worldwide.

set -e

cat<<EOF > left-recursive-parse-of-a-double-subtraction.mp
prologues:=2;
verbatimtex
\documentclass{article}
\begin{document}
etex
;

def connect(expr u, v)=
  pair toward;
  toward := unitvector (v - u);
  toward := toward * 8 / abs(ypart toward);
  draw (u+toward)--(v-toward);
enddef;

beginfig(0)
  pickup pencircle;
  xs := 60;
  ys := 30;
  pair a[];
  a0 := (0, 0) xscaled xs yscaled ys;
  a1 := (-1, -1) xscaled xs yscaled ys;
  a2 := (0, -1) xscaled xs yscaled ys;
  a3 := (1, -1) xscaled xs yscaled ys;
  a4 := (-2, -2) xscaled xs yscaled ys;
  a5 := (-1, -2) xscaled xs yscaled ys;
  a6 := (0, -2) xscaled xs yscaled ys;
  a7 := (2, -2) xscaled xs yscaled ys;
  a8 := (-2, -3) xscaled xs yscaled ys;
  a9 := (0, -3) xscaled xs yscaled ys;
  a10 := (2, -3) xscaled xs yscaled ys;
  a11 := (-2, -4) xscaled xs yscaled ys;
  a12 := (0, -4) xscaled xs yscaled ys;
  a13 := (-2, -5) xscaled xs yscaled ys;
  label(btex \(\mathit{Expression}\) etex, a0);
  label(btex \(\mathit{Expression}\) etex, a1);
  label(btex \(-\) etex, a2);
  label(btex \(\mathit{Term}\) etex, a3);
  label(btex \(\mathit{Expression}\) etex, a4);
  label(btex \(-\) etex, a5);
  label(btex \(\mathit{Term}\) etex, a6);
  label(btex \(\mathit{Factor}\) etex, a7);
  label(btex \(\mathit{Term}\) etex, a8);
  label(btex \(\mathit{Factor}\) etex, a9);
  label(btex \(\mathit{Integer}\) etex, a10);
  label(btex \(\mathit{Factor}\) etex, a11);
  label(btex \(\mathit{Integer}\) etex, a12);
  label(btex \(\mathit{Integer}\) etex, a13);
  connect(a0, a1);
  connect(a0, a2);
  connect(a0, a3);
  connect(a1, a4);
  connect(a1, a5);
  connect(a1, a6);
  connect(a3, a7);
  connect(a4, a8);
  connect(a6, a9);
  connect(a7, a10);
  connect(a8, a11);
  connect(a9, a12);
  connect(a11, a13);
endfig;

bye;
EOF

cat<<EOF > left-recursive-parse-of-a-double-subtraction.tex
\documentclass{article}
\usepackage[paperwidth=22cm,paperheight=13cm,text={22cm,13cm}]{geometry}
\usepackage{graphicx}
\pagestyle{empty}
\begin{document}
\hbox{}
\centerline{\convertMPtoPDF{\jobname.0}{2}{2}}
\end{document}
EOF

mpost left-recursive-parse-of-a-double-subtraction
pdflatex left-recursive-parse-of-a-double-subtraction
convert left-recursive-parse-of-a-double-subtraction.pdf left-recursive-parse-of-a-double-subtraction.png