Explain why abs does not generate events.

chapters/operatorsandexpressions.tex

@@ -433,6 +433,13 @@ \subsection{Numeric Functions and Conversion Functions}\label{numeric-functions-
 Expands into \lstinline!noEvent(if $v$ >= 0 then $v$ else -$v$)!.
 Argument $v$ needs to be an \lstinline!Integer! or \lstinline!Real! expression.
 \end{semantics}
+\begin{nonnormative}
+The reason this does not generate events is that in many cases that introduced more problems than it solves.
+A typical case is a flow equation of the form \lstinline!abs(x)*x=y!.
+If we have to solve for \lstinline!x! and had events for \lstinline!abs(x)! we would not find a solution if \lstinline!y! passes through zero.
+
+In inverted form this equation is \lstinline!x=sign(y)*sqrt(abs(y))!, with similar issues.
+\end{nonnormative}
 \end{functiondefinition}
 
 \begin{functiondefinition}[sign]