--- a/slides/slides04.tex	Sun Oct 27 11:31:08 2019 +0000
+++ b/slides/slides04.tex	Sun Oct 27 11:46:06 2019 +0000
@@ -985,7 +985,7 @@
 \item new regex: \bl{$(x:r)$}\hspace{7mm}new value: \bl{$Rec(x,v)$}\medskip\pause
 
 \item \bl{$nullable(x:r) \dn nullable(r)$}
-\item \bl{$der\,c\,(x:r) \dn (x:der\,c\,r)$}
+\item \bl{$der\,c\,(x:r) \dn der\,c\,r$}
 \item \bl{$mkeps(x:r) \dn Rec(x, mkeps(r))$}
 \item \bl{$inj\,(x:r)\,c\,v \dn Rec(x, inj\,r\,c\,v)$}
 \end{itemize}\bigskip\bigskip\pause