Haskell library of efficent, purely-functional data structures

 The abstract interface (API) of the Edison library for Haskell for
 use with ghc.
 .
 Edison is a library of purely function data structures for Haskell
 originally written by Chris Okasaki. Conceptually, it consists of two
 things:
   - A set of type classes defining data the following data structure
     abstractions: 'sequences', 'collections' and 'associative
     collections'
   - Multiple concrete implementations of each of the abstractions
 .
 This package contains the set of type classes.