[Haskell-cafe] design question: decision tree from "Programming Collective Intelligence"

[Stephen Tetley]

Hello

Maybe "permutation trees" are a viable starting point?

See the paper "Parsing Permutation Phrases" which appears to be on CiteSeer.

Some slides are also here - the data type definitions and Functor
instance for permutation trees are on page 18 (pdf index page 19):
http://www.comlab.ox.ac.uk/jeremy.gibbons/wg21/meeting56/loeh-slides.pdf

An alternative implementation for applicative functors is here:
http://hackage.haskell.org/package/action-permutations

Note the use of existentials here is pretty cunning, I didn't get very
far the time I attempted to use the technique for my own purposes.

Best wishes

Stephen