exists

This package contains: Existential datatypes for holding evidence of constraints on types of kind * and * -> *; Type classes for existential datatypes holding evidence of constraints on types of kind * and * -> *; Completely useless existential datatypes holding evidence of no constraint on types of kind * and * -> *; Assorted type class instances for the above; A type-level combinator for combining constraint constructors. (Some of these might be better off as separate packages.) Data.Exists has most of the important things. Minimum GHC: 7.4 Changes in 0.2: Removed Comonad-related things (they were probably useless anyways) Added Data.Exists.CPS