Proposal: parametrize tree stem container type in containers

[M Farkas-Dyck]

A few years ago I uploaded the package generic-tree to Hackage (before I knew the customary version scheme, sorry about that) which has trees parametrized over stem container type:

data Tree v a = Node a (v (Tree v a))

As this is a functional superset of the containers tree, I think it appropriate to include in containers, which I hereby propose.

Ultimately, if this is accepted, I would like to define the list-specialized tree in terms of this.