[Haskell-cafe] Re: [off-topic] OOPer?

Jonathan Cast jonathanccast at fastmail.fm
Mon Nov 17 19:04:54 EST 2008

On Mon, 2008-11-17 at 21:49 -0200, Maurí­cio wrote:
> >  (...)  I don't recall where I found the following example, but copied
>  > it locally as compelling evidence  that the functional solution can be
>  > much clearer and  shorter than the same solution  modeled with objects
>  > and inheritance.
> Greg,
> I desagree with you.  Bjarne Stroustrup, the original creator of C++, is
> a sensible person

I think his creation of C++ is evidence against that view...

>  and I share his peacefull opinion in this matter:
> http://www.research.att.com/~bs/bs_faq.html#compare
> Even with good  intentions, I've never seen such  kind of comparison not
> to fall into religious fights.

How do you recommend selecting a language?  Stroustrup, in my
experience, seems to think the answer is `any method but technical
merits', which would make me suspicious of the technical merits of his
solution even if I knew nothing else about them (and I know all too
much...).  Ask yourself: what is he hiding?

>  > -- Arithmetic expression forms data Expr = Num Int | Add Expr Expr
>  >
>  > -- Evaluate expressions
>  > eval :: Expr -> Int
>  > (...)
>  > public abstract class Expr {
>  >    public abstract int eval ();
>  >    public abstract void modn(int v);
> Although I'm not good enough to judge anyone's Haskell code, the Haskell
> version  seems nice.  I  don't  know how  someone  who understands  well
> object-oriented code  would do  that. But I  did C++ until  around 1998,
> when the first standard was set, and  I can tell you for sure that, even
> at that  time, no one who  knows at least  the basics of C++  would ever
> write that problem like this.

Of course not.  But their solution wouldn't be object-oriented, either;
this is just an example where OO solutions don't make sense.  (And the
example code is Java; I've been wracking my brain, but I can't come up
with any other way to do it in that language).


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