Re: [Haskell-cafe] Solved but strange error in type inference

On Wed, Jan 4, 2012 at 2:48 AM, Bardur Arantsson wrote:

'subsome' to a different type than the one you intended -- and indeed one which can't be unified with the inferred type. (Unless you use ScopedTypeVariables.)

Thanks for the reply. Actually, my question is why the different type can't be unified with the inferred type? Could you point me some related resources?