Interesting article on types

What a coincidence! Just when the students are pulling their hairs trying to grasp the concept of interfaces in Java, I came across this well written, comprehensive article explaining type, data abstraction and polymorphism. These concepts are presented rather theoretically, but quite easy to understand as the authors relate them to features in programming languages.

Highly recommended!

The link is:

http://www.google.co.uk/url?sa=t&source=web&ct=res&cd=1&ved=0CAcQFjAA&url=http%3A%2F%2Flucacardelli.name%2FPapers%2FOnUnderstanding.A4.pdf&rct=j&q=type+abstraction+and+polymorphism&ei=NI38Sve3O82hjAf62ZCDBw&usg=AFQjCNE14l1vDd7Ok9hdRMpdxTZzH_tuOw&sig2=JRr6vTbCuZfRB7gRXB5NKg