Additional part of #2204

This is not ideal.

chapters/arrays.tex

@@ -413,9 +413,11 @@ \subsection{Reduction Functions and Operators}\doublelabel{reduction-functions-a
 \begin{tabular}{@{}p{10cm}@{}}
 Also described in \autoref{reduction-expressions}\\
 Returns the sum of the expression e(i, ..., j) evaluated for all
-combinations of i in u, ..., j in v: e(u{[}1{]},...
+combinations of i in u, ..., j in v: For integer indexing this is
+  e(u{[}1{]},...
   ,v{[}1{]})+e(u{[}2{]},... ,v{[}1{]})+... +e(u{[}end{]},...
   ,v{[}1{]})+...+e(u{[}end{]},... ,v{[}end{]})
+  For non-integer indexing this uses all valid indices instead of 1..end.
   The type of sum(e(i, ..., j) for  i in u, ..., j
     in v) is the same as the type of e(i,...j).
 \end{tabular}\\ \hline
@@ -434,11 +436,12 @@ \subsection{Reduction Functions and Operators}\doublelabel{reduction-functions-a
 \begin{tabular}{@{}p{10cm}@{}}
 Also described in \autoref{reduction-expressions}.\\
 Returns the product of the scalar expression e(i, ..., j) evaluated for
-all combinations of i in u, ..., j in v:
+all combinations of i in u, ..., j in v: For integer indexing this is
 \begin{lstlisting}[language=modelica]
   e(u[1],...,v[1])*e(u[2],...,v[1])*...
   *(u[end],...,v[1])*...*e(u[end],...,v[end])
 \end{lstlisting}
+  For non-integer indexing this uses all valid indices instead of 1..end.
   The type of product(e(i, ..., j) for  i in u, ..., j
     in v) is the same as the type of e(i,...j).
 \end{tabular}