Fix hard-coded references in listing

chapters/functions.tex

@@ -619,7 +619,7 @@ \subsubsection{Function Partial Application}\label{function-partial-application}
 
 \begin{example}
 Function partial application of a function that is a component, according to case~\ref{functional-argument:component-partial-application} above:
-\begin{lstlisting}[language=modelica]
+\begin{lstlisting}[language=modelica,escapechar=!]
 partial function SurfaceIntegrand
   input Real x;
   input Real y;
@@ -634,7 +634,7 @@ \subsubsection{Function Partial Application}\label{function-partial-application}
   output Real z;
 algorithm
   z := quadrature(y1, y2, function integrand(y = x));
-  // This is according to case (d) and needs to bind the 2nd argument
+  // This is according to case !\ref{functional-argument:component-partial-application}! and needs to bind the 2nd argument
 end quadratureOnce;
 
 function surfaceQuadrature
@@ -648,7 +648,7 @@ \subsubsection{Function Partial Application}\label{function-partial-application}
   integral :=
     quadrature(x1, x2,
       function quadratureOnce(y1 = y1, y2 = y2, integrand = integrand));
-  // Case (b) and (c)
+  // Case !\ref{functional-argument:partial-application}! and !\ref{functional-argument:component}!
 end surfaceQuadrature;
 \end{lstlisting}
 \end{example}