Math & Science ⇒ context free grammar

[krislodz]

Hello,
I need to do type setting of simple context-free grammar. i could not find any useful packages dedicated for that. Are there any such packages ?

[gmedina]

Hi,

can you please attach (or provide a link to) an image showing the kind of things that you want to do?

[krislodz]

Grammar printout as in following image

img23.gif (1020 Bytes) Viewed 9602 times

Designed for simple subset of C language.

[gmedina]

You can use something like the following:

Code: Select all

\documentclass{article}
\usepackage{amsmath}
\usepackage{array}
\usepackage{txfonts}

\begin{document}

{\setlength\tabcolsep{4pt}
\begin{tabular}{>{$}l<{$}>{$}r<{$}>{$}l<{$}}
  R &\Coloneqq & R\\
  &| &R_\ast\\
  &| &(R)\\
  &| &a\\
  &| &b
\end{tabular}}

\end{document}

[krislodz]

Thanks gmedina, I managed to typeset the grammar that i use. It does not look as good as it could though, the nonterminals like Ss and Fs are separated by unwanted spaces. Any idea how to improve it ?

Code: Select all

\documentclass{article}
\usepackage{amsmath}
\usepackage{array}
\usepackage{txfonts}

\begin{document}

{\setlength\tabcolsep{4pt}
\begin{tabular}{>{$}l<{$}>{$}r<{$}>{$}l<{$}}
  e &\Coloneqq &n\\
  &| &x\\
  &| &e_1 \; op_b \; e_2\\
  &| &op_m \; e\\
  &| &(e)\\
  &| &f(es)\\
  es &\Coloneqq &e\\
  &| &e, \; es\\
  S &\Coloneqq &x := e;\\
  &| &skip;\\
  &| &read \; x;\\
  &| &write \; e;\\
  &| &return \; e;\\
  &| &if(e) \; S_1 \; else \; S_2\\
  &| &while(e) \; S\\
  &| &\{Ds \; Ss\}\\
  &| &\{Ss\}\\
  Ss &\Coloneqq &S\\
  &| &S \; Ss\\
  Ds &\Coloneqq &T \; x;\\
  &| &T \; x; Ds\\
  Fs &\Coloneqq &T \; f(Ds)\{Ss\}\\
  &| &T \; f(Ds)\{Ss\} \; Fs\\
  T &\Coloneqq &int\\
  &| &float\\
  P &\Coloneqq &program \; Ds \; Fs \; Ss \; end
\end{tabular}}

$op_b \in \{\&,|,<,>,+,-,*,/\}, op_m \in \{!,-\}$

\end{document}

[gmedina]

Hi,

certain combinations of characters will produce that unwanted space. In the code below I defined the new command \nonter that corrects the problem:

Code: Select all

\documentclass{article}
\usepackage{amsmath}
\usepackage{array}
\usepackage{txfonts}

\newcommand\nonter[1]{\ensuremath{#1\negthinspace s}}

\begin{document}

{\setlength\tabcolsep{4pt}
\begin{tabular}{>{$}l<{$}>{$}r<{$}>{$}l<{$}}
  &| &\{Ds \; Ss\}\\% bad spacing
  &| &\{Ds \; \nonter{S} \}\\% corrected spacing
  &| &\{Ds \; Fs\}\\% bad spacing
  &| &\{Ds \; \nonter{F} \}% corrected spacing
\end{tabular}}

\end{document}

Of course, instead of \negthinspace you can use \negthickspace or even \hspace*{<value>}, where <value> can be any valid length (in your case, negative).

[krislodz]

Thanks a lot gmedina for help again. Kind of strange that there is no package for printing grammars built-in.