I am pleased to announce version 0.2 of the package tree-monad that provides instances of MonadPlus that represent the search space of non- deterministic computations as a tree. In version 0.2 I have implemented an optimized CPS version of the tree monad based on the idea described in "Asymptotic Improvement of Computations over Free Monads" [^1]. The package is on Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/tree-monad The sources are on Github: http://github.com/sebfisch/tree-monad Installation and usage instructions are at: http://sebfisch.github.com/tree-monad A possible application of search trees is parallel search as described in the blog post: http://www-ps.informatik.uni-kiel.de/~sebf/haskell/speedup-search-with-paral... The package parallel-tree-search by Fabian Reck and myself http://hackage.haskell.org/cgi-bin/hackage-scripts/package/parallel-tree-sea... implements the search described in the above blog post based on the hereby announced package tree-monad. Cheers, Sebastian [^1]: http://wwwtcs.inf.tu-dresden.de/~voigt/mpc08.pdf