libghc-unordered-containers-doc 0.2.5.1-4build1 (amd64 binary) in ubuntu xenial

 It contains efficient hashing-based container types. The containers
 have been optimized for performance critical use, both in terms of
 large data quantities and high speed.
 .
 The declared cost of each operation is either worst-case or
 amortized, but remains valid even if structures are shared.
 .
 This package provides the documentation for a library for the Haskell
 programming language.
 See http://www.haskell.org/ for more information on Haskell.