What about replacing

> Haskell provides indexable arrays, which may be thought of as functions whose domains are isomorphic to contiguous subsets of the integers.

with

> Haskell provides indexable arrays, which are functions on the domain [0, ..., k-1]?

Or is the domain actually anything "isomorphic to contiguous subsets of the integers"?

That is typical in most languages, but Haskell's Data.Array is actually parametric over both the index type and the element type, with the index type required to provide a mapping to contiguous integers. This makes it similar to eg. a hashmap which is parametric over both key and element types, with the key type required to provide hashing.