On 4 May 2011 07:25, Federico Mastellone <fmaste@gmail.com> wrote:

Because the underlying structure is already Foldable, so why creating
a dummy function for every method on the Foldable class that only
calls the same function but in the underlying structure.

If you make your MultiMap type and instance of Foldable, you get every method on the Foldable class for free anyway. Namely, you do not need to replicate functions with a Foldable constraint with your MultiMap data type.