The Digitalk Smalltalk programming style guide had an item titled: "Never
use an array where an object will do".

The basic idea is that if you've reached the point where you need to
communicate some sort of heterogeneous aggregation then its time to define
a new class of object. It may seem like a heavyweight approach but down
stream you will most likely be glad you used a new class. Maintainers of
your code will certainly appreciate it.

A few years ago, Juanita Ewing wrote a Smalltalk Report article on this
subject. It can be found at:
http://www.smalltalksystems.com/publications/misuse_of_arrays.doc
Microsoft Word is required to read the article.

Allen_Wirfs-Brock at Instantiations.com