[Haskell] Fixpoint combinator without recursion
stefanor at cox.net
Wed Apr 4 16:41:21 EDT 2007
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
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