Haskell implementation of queryable sets - GHC libraries

 IxSet is a Haskell efficient implementation of queryable sets: it
 makes you able to define complex data types and index them on some of
 theirs fields. Then you can efficiently query the IxSet to find the
 records that satisfy some condition.
 .
 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.