Add semantics of general subscripting.

chapters/arrays.tex

@@ -55,6 +55,7 @@ \section{Array Declarations}\label{array-declarations}
 \item
   Binding equations of the form \lstinline!x1 = x2! are allowed for arrays independent of whether the index types of dimensions are subtypes of \lstinline!Integer!, \lstinline!Boolean!, or enumeration types.
 \end{itemize}
+Operations constructing arrays (e.g., matrix multiplication, indexing, array constructors) only generate arrays index by \lstinline!Integer!.
 
 % IMPROVETOP
 \begin{table}[H]
@@ -946,6 +947,9 @@ \section{Indexing}\label{array-indexing}\label{indexing}
 The number of dimensions of the expression is reduced by the number of scalar index arguments.
 If the number of index arguments is smaller than the number of dimensions of the array, the trailing indices will use `\lstinline!:!'.
 
+It is possible to index a general expression by enclosing it in parenthesis.
+Note that the grammar is left factored and allows indexing of \lstinline[language=grammar]!output-expression-list!, but only indexing of an expression is syntactically valid.
+
 It is also possible to use the array access operator to assign to element/elements of an array in algorithm sections.
 This is called an \firstuse[assignment statement!indexed]{indexed assignment statement}.
 If the index is an array the assignments take place in the order given by the index array.