Name: Anonymous 2014-04-03 9:38
Haskell has an explicit goal (according to Simon Peyton Jones) of minimizing the pain of strict static typing - of having the fewest possible cases where what you want to express is reasonable but doesn't fit the type system. The useful cases that OOP supports but Haskell 98 didn't are already supported (in a different way) in Haskell via extensions. In fact the modern Haskell typesystem is far superior to anything I know of in the OOP world.
So basically, you just don't need OOP in Haskell. You could do things using Haskell 98 typeclasses that you couldn't do with OOP anyway, and with (stable, widely used) extensions such as higher-rank and existential types you can now do pretty much anything you could with OOP. With multi-parameter typeclasses and type functions, you can go beyond OOP to handle what Java generics can do (probably more, though I'm not that familiar with Java) and a fair chunk of what C++ template classes can. And that's without looking at Template Haskell.
There are some cases where OOP still seems a bit more convenient, but mostly that's a short-term gain that's outweighed by longer-term losses. For example OOP can be a lot more convenient at times because of the pervasive mutability, but Haskell keeps mutability under control for a reason.
So basically, you just don't need OOP in Haskell. You could do things using Haskell 98 typeclasses that you couldn't do with OOP anyway, and with (stable, widely used) extensions such as higher-rank and existential types you can now do pretty much anything you could with OOP. With multi-parameter typeclasses and type functions, you can go beyond OOP to handle what Java generics can do (probably more, though I'm not that familiar with Java) and a fair chunk of what C++ template classes can. And that's without looking at Template Haskell.
There are some cases where OOP still seems a bit more convenient, but mostly that's a short-term gain that's outweighed by longer-term losses. For example OOP can be a lot more convenient at times because of the pervasive mutability, but Haskell keeps mutability under control for a reason.