\documentclass{article}
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\usepackage{overture}
\newcommand{\StateDef}[1]{{\bf #1}}
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\title{A crosswords assistant}
\author{Yves LEDRU\footnotemark}
\date{March 14, 1995}
\begin{document}
\maketitle
\footnotetext{Laboratoire de G\'enie Informatique - Institut IMAG (UJF - INPG-
CNRS), BP
53x 38041 Grenoble
Cedex (FRANCE) - Tel + 33 76827214 - Fax + 33 76446675 - e-mail
[email protected]}
This tutorial example is taken out of a VDM course given
to the students of the Dipl\^{o}me d'Etudes Sup\'erieures Sp\'ecialis\'ees en
G\'enie Informatique (5th year) at the Universit\'e Joseph Fourier.
This
example uses the implicit style of specification of VDM-SL and thus may not be
executed with the IFAD toolbox.
\section{Informal statement}
The crosswords assistant is a simple system which helps writing crosswords.
Its user places words or black squares on a a crossword grid.
The system helps him keep a log of the words that appear on the grid.
These words appear in a list of words (waiting list).
The user will then informally check that these words effectively exist. Once a
word has been checked by the user, it will be validated and stored in a second
list.
\subsection*{Example}
The user has placed sucessively the words {\tt word}, {\tt coal} and {\tt art}
on the grid.
\vspace{0.5cm}
{\tt \begin{tabular}{r|c|c|c|c|c|c|c|c|}
& 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8\\
\hline
1 & & & & & & & & \\
\hline
2 & & & & & & & & \\
\hline
3 & & & &w& & & & \\
\hline
4 & & &c &o &a &l & & \\
\hline
5 & & &a &r&t & & & \\
\hline
6 & & & &d& & & & \\
\hline
7 & & & & & & & & \\
\hline
8 & & & & & & & & \\
\hline
\end{tabular}}
\vspace{0.5cm}
As a result, the words {\tt at} and {\tt ca} are also on the grid. The list of
words to validate is thus:
\begin{itemize}
\item[ ] words to validate : {\tt word, coal, art, at, ca}
\end{itemize}
The user then checks in his (paper) dictionary that all words but {\tt ca} are
english words. The two lists become:
\begin{itemize}
\item[ ] words to validate : {\tt ca}
\item[ ] valid words : {\tt word, coal, art, at}
\end{itemize}
In the sequel, the list of words to validate will also be referred to as the
``waiting list''.
\newpage
The user may now add the word {\tt cord} to the grid.
\vspace{0.5cm}
{\tt \begin{tabular}{r|c|c|c|c|c|c|c|c|}
& 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8\\
\hline
\multicolumn{9}{l}{\ldots}\\
\hline
3 & & & &w& & & & \\
\hline
4 & & &c &o &a &l & & \\
\hline
5 & & &a &r&t & & & \\
\hline
6 &c &o &r &d& & & & \\
\hline
\multicolumn{9}{l}{\ldots}\\
\end{tabular}}
\vspace{0.5cm}
{\tt ca} has now disappeared from the grid and the waiting list
is updated accordingly.
\begin{itemize}
\item[ ] words to validate : {\tt car, cord}
\item[ ] valid words : {\tt word, coal, art, at}
\end{itemize}
Other operations on the grid include:
\begin{itemize}
\item adding ``black'' squares
\item deleting some letters
\end{itemize}
The objective of the user is to fill in the whole grid with either black
squares or letters and to end up with an empty waiting list.
\include{generated/latex/specification/crossword.vdmsl}
\end{document}
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