RE: [Haskell-cafe] Is there anyone out there who can translate C# generics into Haskell?

3 Jan 2008

      [snip]
...
-- C#: interface IX1 { String foo1(int); }
class IX1 obj where 
 foo1 :: Int -> obj -> String
Yep...I think that's what I'd do....though I would have done...

"foo1 :: obj -> Int -> String"

Does that matter?
...
-- C#: interface IX2<A> { String foo2(A); }
class IX2 obj a where 
 foo2 :: a -> obj -> String
Ok same here
...
--C#: interface IX3<A> where A : IY { String foo3(A); }
class IY a where {- ... -}
class IY a => IX3 obj a where 
 foo3 :: a -> obj -> String
Yep I think again I would have guessed at that
...
--C#: interface IX4<A> : IZ where A : IY
class IZ a where {- ... -}
class (IY a, IZ obj) => IX4 obj a where
 foo4 :: a -> obj -> String
Hmmmm...this would have been one of my guesses....but let me have a
go...
...
This assumes your "objects" are immutable, otherwise you would have to
return (obj,String) instead of just String and then you most likely
want to
use the state monad and "do notation" to make functional programming
look
more like imperative programming.
This is fine....my oop is largely immutable.
...
You really have to drop the OO way of thinking, 
which I find the hardest :)
Haskell's type classes are more powerful in some sense than C#
interfaces;
for example, in C# you can't attach an interface to any class (take for
example the Point struct), it has to be your own class, while in
Haskell,
you can implement an instance of a type class for any datatype!
OK but I was going to go onto 

Interface IX<A> 
	where A : IX<A>
{
}

And 

Interface IX 
	where A : B
{
}

Where I cannot see a way to do the above in Haskell at all....as
interfaces effectively operator on type classes not types....which seems
inherently more powerful

But if these could be done in Haskell the see what could be made of
stuff like....which is obviously problematic in C# it obviously doesn't
work....but potentially does make 'sense'.

Interface IX<A> : A
{
}
...
Hope this helps a bit. As I'm new myself to Haskell, so take this with
a
"grain of salt".
It does...I will have a go with your sample answers.
...
Once you bite the bullet, I found Haskell a lot more fun than C#,
although
C# of course comes with a gigantic .NET framework and tools...
I'm looking at Haskell because of the formality of it's type
system....but I'm actually not convinced it is as powerful as an OO
one....i.e. OO ones operatate principally (in Haskell speak) on "type
classes" not "types"
...
Peter
-----Original Message-----
From: haskell-cafe-bounces@haskell.org
[mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Nicholls, Mark
Sent: Wednesday, January 02, 2008 5:41 PM
To: haskell-cafe@haskell.org
Subject: [Haskell-cafe] Is there anyone out there who can translate C#
generics into Haskell?

I'm trying to translate some standard C# constucts into Haskell... some
of this seems easy....

Specifically

1) 

Interface IX
{
}

2)

Interface IX<A>
{
}

3)

Interface IX<A>
	Where A : IY
{
}

4)

Interface IX<A> : IZ
	Where A : IY
{
}

I can take a punt at the first 2....but then it all falls apart
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe