23 Apr
2003
23 Apr
'03
6:42 a.m.
On Tue, 22 Apr 2003 23:05:09 +0100
Alastair Reid
Unfortunately, in this case, with that function in isolation I get,
Ambiguous type variable(s) `s', `m' in the constraint `MonadState s m' arising from use of `get' ....
An easy way to get round this is to give a completely bogus type signature like:
foo :: a
The compiler will report a mismatch and the error message will tell you what it thinks the type is.
Or the straightforward and simple answer: in GHCi or Hugs, just do :t f. E.g. :t get ==> (MonadState s m) => m s. GHCi (and I imagine Hugs too) doesn't try to validate the constraints.