@hackage dependent-sum0.6.2.2

A dependent sum is a generalization of a particular way of thinking about the Either type. Either a b can be thought of as a 2-tuple (tag, value), where the value of the tag determines the type of the value. In particular, either tag = Left and value :: a or tag = Right and value :: b.

This package allows you to define your own dependent sum types by using your own "tag" types.