Haskell library for Differences lists; profiling libraries

 Differences lists: a list-like type supporting O(1) append.
 This is particularly useful for efficient logging and pretty
 printing, (e.g. with the Writer monad), where list append
 quickly becomes too expensive.
 .
 This package provides a library for the Haskell programming language, compiled
 for profiling. See http://www.haskell.org/ for more information on Haskell.