a map, where the keys may be complex structured data

 This type implements maps where the keys are themselves complex structured
 data. For example, the keys may be the abstract syntax trees for a
 programming language. The map is implemented as a trie, so common parts of
 the keys will be shared in the representation. The library provides a generic
 implementation of the data structure, so values of types that have support for
 'Generic' may be automatically used as keys in the map.
 .
 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.