Merge pull request #2574 from HansOlsson/VariabilityGuarantee

Clarify variability guarantee

Author: HansOlsson

chapters/classes.tex

@@ -408,8 +408,9 @@ \subsection{Component Variability Prefixes discrete, parameter, constant}\double
 \lstinline!enumeration! variables.
 
 \begin{nonnormative}
-A Modelica translator is able to guarantee this property due to
-restrictions imposed on discrete expressions, see \autoref{variability-of-expressions}.
+The restriction that discrete-valued variables (of type \lstinline!Boolean!, etc) cannot be
+declared with continuous-time variability is one of the foundations of the expression variability rules
+that will ensure that any discrete-valued expression has at most discrete-time variability, see \autoref{variability-of-expressions}.
 \end{nonnormative}
 
 The variability of expressions and restrictions on variability for