[Haskell] Fixpoint combinator without recursion

[Stefan O'Rear]

On Wed, Apr 04, 2007 at 01:36:18PM -0700, Michael Vanier wrote:
> For those of us who aren't type theorists: What's a "negative datatype"?

Negative isn't the usual term; we mostly call them 'contravariantly
recursive' data types, due to CT influence.  Anyways the thing to note
is that the value appears recursively, on the left of an arrow. 


data Foo = Foo (Foo -> Bool)   -- contravariantly recursive
data Foo = Foo (Bool -> Foo)   -- covariantly recursive

Stefan