On Sun, Nov 1, 2009 at 2:00 AM, Michael Vanier
<mvanier42@gmail.com> wrote:
Gregory Collins wrote:
Tom Davie <tom.davie@gmail.com> writes:
On 10/31/09, Magicloud Magiclouds <magicloud.magiclouds@gmail.com> wrote:
After all, I never think OO as an oppsite way to all other things. The
idea is so general that if you say I cannot use it in Haskell at all,
that would make me feel weird. The only difference between languages
is, some are easy to be in OO style, some are not.
Wow, someone drank the cool aid!
Doing OO-style programming in Haskell is difficult and unnatural, it's
true (although technically speaking it is possible). That said, nobody's
yet to present a convincing argument to me why Java gets a free pass for
lacking closures and typeclasses.
G.
BTW using existential types in Haskell you can mimic OO to a pretty decent degree, at least as far as interfaces are concerned.
I kind of wish we had some convenience notation for doing value-based dispatch like that.... Something like
foo :: [ <Show> ] -> String
foo xs = concatMap show xs
> foo [ 5, True, 1.3 ]
"5True1.3"
(where wrapping a class up in angle brackets makes it into an existentially qualified wrapper, which is instantiated in the class itself -- maybe we need explicit conversion from e.g. Int to <Show> though...)
You don't need it very often, but I wonder if that's because there genuinely isn't a need, or if you tend to avoid writing code in ways which would need it (ask a Java programmer, and they'll probably tell you that the need for type classes and closures don't come up very often - which is clearly untrue for a Haskell programmer).
--
Sebastian Sylvan