I think it's still pretty unclear what this function might do, since the inverse...

kscaldef on Dec 24, 2012 | parent | context | favorite | on: Why learning Haskell makes you a better programmer

I think it's still pretty unclear what this function might do, since the inverse of a map isn't well-defined. I think this is a type signature that makes sense and has a fairly obvious most-likely meaning:

    boo :: Map a b -> b -> Set a

I'm not sure how you would conjure up just an 'a' in general.

Peaker on Dec 24, 2012 [–]

You also need an Ord or at least an Eq constraint on the b's.