Update chapters/functions.tex

Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>

chapters/functions.tex

@@ -316,7 +316,7 @@ \section{Pure Modelica Functions}\label{pure-modelica-functions}
   A \lstinline!when!-statement.
 \item
   \lstinline!pure(impureFunction($\ldots$))! -- which allows calling impure functions in any pure context.
-  Note that the argument to \lstinline!pure! must be a function call, it only applies to the call and not to the arguments of the function call.
+  The wrapping in \lstinline!pure($\ldots$)! only by-passes the purity checking of the callee \lstinline!impureFunction!; the argument expressions of the function call are not affected.
 \item
   Initial equations and initial algorithms.
 \item