Make assertion level a parameter expression

chapters/equations.tex

@@ -459,19 +459,22 @@ \subsection{assert}\label{assert}
 assert(condition, message, assertionLevel);
 assert(condition, message, level = assertionLevel);
 \end{lstlisting}
-
 is an assertion, where \lstinline!condition! is a Boolean expression, \lstinline!message! is a
-string expression, and \lstinline!level! is a built-in enumeration with a default
-value. It can be used in equation sections or algorithm sections.
+string expression, and \lstinline!assertionLevel! is an optional parameter expression of the built-in enumeration type \lstinline!AssertionLevel!.
+It can be used in equation sections or algorithm sections.
 
 \begin{nonnormative}
 This means that assert can be called as if it were a function with three formal parameters, the third formal parameter has the
 name \lstinline!level! and the default value \lstinline!AssertionLevel.error!.
 \end{nonnormative}
 
+\begin{nonnormative}
+A parameter expression is required for \lstinline!level! since it shall be evaluated at compile time.
+\end{nonnormative}
+
 If the \lstinline!condition! of an assertion is true, \lstinline!message! is not evaluated and
-the procedure call is ignored. If the \lstinline!condition! evaluates to false
-different actions are taken depending on the level input:
+the procedure call is ignored. If the \lstinline!condition! evaluates to false,
+different actions are taken depending on the \lstinline!level! input:
 \begin{itemize}
 \item
   \lstinline!level = AssertionLevel.error!: The current evaluation is aborted. The