179 

   179 

   180 \noindent Note also that the convention in Scala is that

   180 \noindent Note also that the convention in Scala is that

   181 \texttt{.r} converts a string into a regular expression. I

   181 \texttt{.r} converts a string into a regular expression. I

   182 leave it to you to ponder whether this regular expression

   182 leave it to you to ponder whether this regular expression

   183 really captures all possible web-addresses. If you need a quick

   183 really captures all possible web-addresses. If you need a quick

   185 \url{https://youtu.be/bgBWp9EIlMM}.

   186 \url{https://youtu.be/bgBWp9EIlMM}.

   186 

   187 

   187 \subsection*{Why Study Regular Expressions?}

   188 \subsection*{Why Study Regular Expressions?}

   188 

   189 

   189 Regular expressions were introduced by Kleene in the 1950ies and they

   190 Regular expressions were introduced by Kleene in the 1950ies and they

   279 

   280 

   280 \begin{center}

   281 \begin{center}

   281 \url{http://davidvgalbraith.com/how-i-fixed-atom/}

   282 \url{http://davidvgalbraith.com/how-i-fixed-atom/}

   282 \end{center}

   283 \end{center}

   283 

   284 

   284 \noindent

   292 \noindent

   285 Such troublesome regular expressions are sometimes called \emph{evil

   293 Such troublesome regular expressions are sometimes called \emph{evil

   286   regular expressions} because they have the potential to make regular

   294   regular expressions} because they have the potential to make regular

   287 expression matching engines to topple over, like in Python, Ruby and

   295 expression matching engines to topple over, like in Python, Ruby and

   288 Java. This ``toppling over'' is also sometimes called

   296 Java. This ``toppling over'' is also sometimes called