Change so that we don't say that there are always discontinuities, an…

…d explain for example.

chapters/operatorsandexpressions.tex

@@ -434,12 +434,13 @@ \subsection{Numeric Functions and Conversion Functions}\label{numeric-functions-
 Argument $v$ needs to be an \lstinline!Integer! or \lstinline!Real! expression.
 \end{semantics}
 \begin{nonnormative}
-By not generating events the property \lstinline!abs($x$)! $\geq 0$ for all $x$ is ensured at the cost of having a derivative that changes discontinuously between events.
+By not generating events the property \lstinline!abs($x$)! $\geq 0$ for all $x$ is ensured at the cost of sometimes having a derivative that changes discontinuously between events.
 
 A typical case requiring the event-free semantics is a flow equation of the form \lstinline!abs(x) * x = y!.
 With event generation, the equation would switch between the two forms \lstinline!x^2 = y! and \lstinline!-x^2 = y! at the events, where the events would not be coinciding exactly with the sign changes of \lstinline!y!.
 When \lstinline!y! passes through zero, neither form of the equation would have a solution in an open neighborhood of \lstinline!y! $= 0$, and hence solving the equation would have to fail at some point sufficiently close to \lstinline!y! $= 0$.
 Without event generation, on the other hand, the equation can be solved easily for \lstinline!x!, also as \lstlinline!y! passes through zero.
+Note that without event generation the derivative of \lstinline!abs(x) * x! never changes discontinuously, despite \lstinline!abs(x)! having a discontinuous derivative.
 
 In inverted form this equation is \lstinline!x = sign(y) * sqrt(abs(y))!.
 With event generation, the call to \lstinline!sqrt! would fail when applied to a negative number during root finding of the zero crossing for \lstinline!abs(y)!, compare \cref{events-and-synchronization}.