26 Sep
2001
26 Sep
'01
11:57 a.m.
nhc doesn't like the following program ...
type Option = Maybe
f :: Option a -> Maybe a f = id
Yes, nhc98's type checker doesn't do kind inference, so the definition of a type synonym must have the same kind as all its uses.
The problem disappears if we change the type definition to
type Option a = Maybe a
Indeed. Regards, Malcolm