14 Apr
2010
14 Apr
'10
4:29 a.m.
On 14 Apr 2010, at 09:25, Ashley Yakeley wrote:
Thomas Davie wrote:
Because we consider that the Functor laws must hold for all values in the type (including bottom).
This is not so for IO, which is an instance of Functor. "fmap id undefined" is not bottom.
It isn't? fPrelude> fmap id (undefined :: IO ()) *** Exception: Prelude.undefined Bob