Clarify how to deduce array size (from binding equation and attributes).

Closes #2212

chapters/arrays.tex

@@ -40,9 +40,13 @@ \section{Array Declarations}\doublelabel{array-declarations}
 built-in type classes Real, Integer, Boolean, String, and enumeration
 types. The type of a dimension upper bound expression, e.g. n, m, p,...
 in the table below, need to be a subtype of Integer or EB for a class EB
-that is an enumeration type or subtype of the Boolean type. Colon (:)
+that is an enumeration type or subtype of the Boolean type. 
+
+Colon (:)
 indicates that the dimension upper bound is unknown and is a subtype of
-Integer.
+Integer. The size of such a variable can be determined from its binding equation, or the size
+of any of its array attributes - see also \autoref{flexible-array-sizes-and-resizing-of-arrays-in-functions}.
+The size cannot be determined from other equations or algorithm.
 
 Upper and lower array dimension index bounds are described in \autoref{array-dimension-lower-and-upper-index-bounds}.