It is a continuation-based, backtracking, logic programming monad. An
 adaptation of the two-continuation implementation found in the paper
 Backtracking, Interleaving, and Terminating Monad Transformers available
 here: http://okmij.org/ftp/papers/LogicT.pdf
 .
 This package provides the documentation for a library for the Haskell
 programming language.
 See http://www.haskell.org/ for more information on Haskell.