471 \noindent

   471 \noindent

   472 We have the following correspondence between 

   472 We have the following correspondence between 

   473 derivatives on regular expressions and

   473 derivatives on regular expressions and

   474 derivatives on a set of strings:

   474 derivatives on a set of strings:

   475 \begin{lemma}\label{derDer}

   475 \begin{lemma}\label{derDer}

   476 	\begin{itemize}

   477 	\begin{itemize}

   477 		\item

   478 		\item

   478 $\textit{Der} \; c \; L(r) = L (r\backslash c)$

   479 $\textit{Der} \; c \; L(r) = L (r\backslash c)$

   479 \item

   480 \item

   480 	$c\!::\!s \in L(r)$ \textit{iff} $s \in L(r\backslash c)$.

   481 	$c\!::\!s \in L(r)$ \textit{iff} $s \in L(r\backslash c)$.

   636 characters, in the meantime constructing a lexing result.

   637 characters, in the meantime constructing a lexing result.

   637 We will introduce the injection phase in detail slightly

   638 We will introduce the injection phase in detail slightly

   638 later, but as a preliminary we have to first define 

   639 later, but as a preliminary we have to first define 

   639 the datatype for lexing results, 

   640 the datatype for lexing results, 

   640 called \emph{value} or

   641 called \emph{value} or

   643 table:

   646 table:

   644 

   647 

   645 \begin{center}

   648 \begin{center}

   646 	\begin{tabular}{c@{\hspace{20mm}}c}

   649 	\begin{tabular}{c@{\hspace{20mm}}c}

   647 		\begin{tabular}{@{}rrl@{}}

   650 		\begin{tabular}{@{}rrl@{}}