[Haskell-cafe] Object Oriented programming for Functional Programmers

[Bob Hutchison]

On 2012-12-30, at 2:58 PM, Daniel Díaz Casanueva <dhelta.diaz at gmail.com> wrote:

> Well, my curiosity is bringing me to learn a new general purpose programming language. Haskellers are frequently comparing Object-Oriented languages with Haskell itself, but I have never programmed in any OO-language! (perhaps this is an uncommon case) I thought it could be good to me (as a programmer) to learn C/C++. Many interesting courses (most of them) use these languages and I feel like limited for being a Haskell programmer. It looks like I have to learn imperative programming (with side effects all over around) in some point of my programming life.
> 
> So my questions for you all are:
> 
> * Is it really worthwhile for me to learn OO-programming?

Yes. And you should learn OO *very* well. And remember, OO doesn't really get interesting until the program gets big.

As for languages I'd suggest Smalltalk or Eiffel, perhaps both. The big advantage to Eiffel is that you have Object Oriented Software Construction (second edition (not first)) to work from. Every OO language has to answer to the issues brought up in OOSC2 (and they don't/can't). Eiffel's inheritance mechanism is also one of the few that let you use inheritance to do useful things (OOSC2 names 16 or 18 different uses for inheritance… it's not just for 'is-a' relationships). Eiffel also has a contract system that's powerful enough to be useful. Smalltalk's advantage is that it will also introduce you to the idea of a programming 'system', for lack of better words. Smalltalk works in a live system, as you are writing code you are modifying live and already executing code. Once you realize that the 'best' editor in Smalltalk is the debugger (and what 'a good debugger' actually means) you'll understand test-driven-development's origins. This is very different from Haskell. Actually, you should probably learn both languages.

I don't think C++ will help you learn OO, or much of anything else either. Vigorously avoid is my advice.

C you're probably going to have to learn sooner or later but wait until you have to. And it's not OO at all. Though, if you learn K&R C (pre-ansi C) you'll get a better understanding of why people liked OO so much :-)

Ruby might be an easy route to OO too. I like the language quite a lot, but I'm not sure I'd recommend it for your purposes.

> 
> * If so, where should I start? There are plenty of "functional programming for OO programmers" but I have never seen "OO programming for functional programmers".
> 
> * Is it true that learning other programming languages leads to a better use of your favorite programming language?

That's been my experience. And it'll be harder to name your favourite language too.

> 
> * Will I learn new programming strategies that I can use back in the Haskell world?

Probably.

Cheers,
Bob

> 
> Thanks in advance for your kind responses,
> Daniel Díaz.
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