Agree. What the author did here is just plain data types, not even abstract data types. Another big mistake in the article is >Classes in an object oriented de

Agree. What the author did here is just plain data types, not even abstract data types. Another big mistake in the article is >Classes in an object oriented design are fundamentally ADTs It isn't. I would suggest the paper Object-Oriented Programming Versus Abstract Data Types by William R. Cook which explains the fundamental differences between the two data abstraction techniques. edit: https://www.cs.utexas.edu/users/wcook/papers/OOPvsADT/CookOOPvsADT90.pdf https://www.cs.utexas.edu/users/wcook/papers/OOPvsADT/CookOO...