Should inheritance (of non-interface types) be removed from programming languages?

Question

This is quite a controversial topic, and before you say \"no\", is it really, really needed?

I have been programming for about 10 years, and I can\'t honestly sa

Answer 1

Of course you can write great programs happily without objects and inheritance; functional programmers do it all the time. But let us not be hasty. Anybody interested in this topic should check out the slides from Xavier Leroy's invited lecture about classes vs modules in Objective Caml. Xavier does a beautiful job laying out what inheritance does well and does not do well in the context of different kinds of software evolution.

All languages are Turing-complete, so of course inheritance isn't necessary. But as an argument for the value of inheritance, I present the Smalltalk blue book, especially the Collection hierarchy and the Number hierarchy. I'm very impressed that a skilled specialist can add an entirely new kind of number (or collection) without perturbing the existing system.

I will also remind questioner of the "killer app" for inheritance: the GUI toolkit. A well-designed toolkit (if you can find one) makes it very, very easy to add new kinds of graphical interaction widgets.

Having said all that, I think that inheritance has innate weaknesses (your program logic is smeared out over a large set of classes) and that it should be used rarely and only by skilled professionals. A person graduating with a bachelor's degree in computer science barely knows anything about inheritance---such persons should be permitted to inherit from other classes at need, but should never, ever write code from which other programmers inherit. That job should be reserved for master programmers who really know what they're doing. And they should do it reluctantly!

For an interesting take on solving similar problems using a completely different mechanism, people might want to check out Haskell type classes.