Add example.

chapters/arrays.tex

@@ -976,6 +976,10 @@ \section{Indexing}\label{array-indexing}\label{indexing}
 v[{j, k}] := {2, 3}; // Same as: v[j] := 2; v[k] := 3;
 v[{1, 1}] := {2, 3}; // Same as: v[1] := 3;
 \end{lstlisting}
+Array indexing of general expression:
+\begin{lstlisting}[language=modelica]
+(a*a)[:, j]    // Vector of the j'th column of a*a
+\end{lstlisting}
 If \lstinline!x! is a vector, \lstinline!x[1]! is a scalar, but the slice \lstinline!x[1:5]! is a vector
 (a vector-valued or colon index expression causes a vector to be returned).
 \end{example}