[Haskell-cafe] Missing Functor instances in GHC 7?

Simon Peyton-Jones simonpj at microsoft.com
Fri Dec 10 09:33:59 CET 2010

| Interestingly, if I import only Control.Applicative from within GHCi, it
| does not find the instances defined in Control.Monad.Instances although
| this module is imported in Control.Applicative. On the other hand, if I
| write a file containing the line 'import Control.Applicative' and load
| this file in GHCi then the instances from Control.Monad.Instances are
| visible.
| Apparently, importing a module in GHCi differs from importing it in a
| Haskell file and loading this into GHCi.

I don't believe that should happen, depending on exactly what you mean by "importing a module in GHCi".

If there's a consensus that the behaviour is wrong, or at least unexpected, would you like to make a reproducible test case and file a ticket?  Thanks!


More information about the Haskell-Cafe mailing list