Clarify nested records. (modelica#3130)

* Clarify nested records.
Closes modelica#3128
* Apply suggestions from code review
Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>

chapters/functions.tex

@@ -2215,17 +2215,16 @@ \subsubsection{Arrays}\label{arrays-1}
 
 \subsubsection{Records}\label{records}
 
-Mapping of record types is only supported for C. A Modelica record class
-that contains simple types, other record elements, is mapped as follows:
+Mapping of record types is only supported for C.
+A Modelica record class is mapped as follows:
 \begin{itemize}
 \item
   The record class is represented by a struct in C.
 \item
-  Each element of the Modelica record is mapped to its corresponding C
-  representation.
+  Each component of the Modelica record is mapped to its corresponding C representation.
+  A nested record component is mapped to a nested struct component.
 \item
-  The elements of the Modelica record class are declared in the same
-  order in the C struct.
+  The components of the Modelica record class are declared in the same order in the C struct.
 \item
   Arrays cannot be mapped.
 \end{itemize}
@@ -2235,16 +2234,24 @@ \subsubsection{Records}\label{records}
 
 \begin{example}
 \begin{lstlisting}[language=modelica]
+record A
+  Integer b;
+end A;
 record R
   Real x;
   Real z;
+  A a1, a2;
 end R;
 \end{lstlisting}
 is mapped to:
 \begin{lstlisting}[language=C]
+struct A {
+  int b;
+};
 struct R {
   double x;
   double z;
+  struct A a1, b2;
 };
 \end{lstlisting}
 \end{example}