RE: Contexts on data type declarations

[Simon Peyton-Jones]

Folks,

Interesting!  Phil, Mark, and Jeff all have a different interpretation of
how contexts on how data type declarations work than I did.  So unless 
some other people chime in, I will therefore adopt their interpretation,
since (a) I'm in the minority and (b) it's not a big deal at all.

But just to make it clear what's under review here, consider

        data Ord a => Tree a = MkTree {
                                          item :: a,
                                          kids :: [Tree a]
                                     }

We know that 
        MkTree :: Ord a => a -> [Tree a] -> Tree a

But what type does the selector 'item' have?  Phil, Mark and Jeff think:

        item :: Ord a => Tree a -> a

The same would apply to any use of MkTree in a pattern.  For example:

        f (MkTree _ _) = True

would get the type

        f :: Ord a => Tree a -> Bool

Speak now or put up with overloaded selectors!

Simon