Attempt

chapters/classes.tex

@@ -387,7 +387,9 @@ \subsection{Component Variability Prefixes discrete, parameter, constant}\label{
 The \lstinline!Real! variables declared with the prefix \lstinline!discrete! is a subset of the discrete-time \lstinline!Real! variables.
 For a \lstinline!Real! variable, being discrete-time is equivalent to being assigned in a when-clause.
 A variable used as argument to \lstinline!pre! outside a when-clause must be discrete-time.
-Tools may optimize code to only compute piecewise constant variables at events.
+Tools may optimize code to only compute piecewise constant variables at events starting from discrete-time expressions.
+There might be also variables that are piecewise constant, but change at times that are not events.
+It is not clear how a tool could detect and optimize such cases.
 
 \begin{lstlisting}[language=modelica]
 model PiecewiseConstantReals