(...) 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 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. (Although I'm not more than just a humble language user.)
-- 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. Best, Maurício