In a lot of cases though annotating all the recursive aspects with newtypes
is a _royal_ pain, and is even worse if you want the datatypes to be
instances of common type classes like Functor, Applicative, etc... (try it
sometime)
I don't advocate allowing infinite types wholesale, just in specific cases
with a special annotation (like a type signature specifying the allowed
infinite type). I think this would be the best of both worlds.
- Job
On Tue, Aug 4, 2009 at 4:23 AM, Heinrich Apfelmus wrote: Job Vranish wrote: I think that in an ideal world haskell would have some way of allowing
infinite types if you asked for them explicitly (say in the type somehow) and then just automatically wrap/unwrap everything with newtypes
behind the scenes (well maybe in an ideal world it wouldn't have to do signature
this either). This wouldn't change the underlying semantics, but would get rid
of
alot of messyness. Infinite types are possible, My toy language infers infinite types just
fine
:) and I think Ocaml has an option for them, but niether of those have
type
classes so I'm not sure how compatable the idea is with haskell in
general. There was a thread with a compelling reason against vanilla infinite
types some time ago: http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17103 Of course, you can have all the recursion you want by using newtype ,
it's just that you need to annotate them with the extraneous
constructor. In fact, that's exactly the purpose of the constructor;
think of it as an aid for the type checker. Regards,
apfelmus --
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