Search problem solutions using generalised search functions

searchSolutions.hs

import SearchPath -- https://gist.github.com/2667320


-- Missionaries and Cannibals
mc = let start = ((3, 3, 1, 0, 0, 0), "")

         isGoal (state, _) = state == (0, 0, 0, 3, 3, 1)

         action m c = (take m (repeat 'M')) ++ (take c (repeat 'C'))

         successors ((m1, c1, b1, m2, c2, b2), _)

            | c1 > m1 && m1 > 0 || c2 > m2 && m2 > 0 = [] 

            | b1 > 0 = [((m1 - m, c1 - c, b1 - 1, m2 + m, c2 + c, b2 + 1), (action m c) ++ "->") | 
                        m <- [0 .. m1 + 1], 
                        c <- [0 .. c1 + 1], 
                        m + c > 0, m + c < 3]

            | b2 > 0 = [((m1 + m, c1 + c, b1 + 1, m2 - m, c2 - c, b2 - 1), "<-" ++ (action m c)) | 
                        m <- [0 .. m1 + 1], 
                        c <- [0 .. c1 + 1], 
                        m + c > 0, m + c < 3]

            | otherwise = []

     in shortestPath successors isGoal start

    
-- Snake Cube Puzzle
snakes = let directions = [[1,0,0], [-1,0,0], [0,1,0], [0,-1,0], [0,0,1], [0,0,-1]]

             outOfBounds x = x < 0 || x > 2

             getSwivel dir = [dir' | 
                              dir' <- directions, 
                              dir' /= dir, 
                              dir' /= (map negate dir)]
                                
             start = ([0,0,0], ([1,0,0], "001110110111010111101010100"))
             
             isGoal (_, (_, blocks)) = length blocks == 1

             successors (coord, (dir, (b : blocks)))

                        | any outOfBounds coord = []
                        
                        | otherwise = let dirs = case b of 
                                                      '0' -> [dir]
                                                      '1' -> getSwivel dir

                                      in [(coord', (d, blocks)) | 
                                          d <- dirs,
                                          let coord' = zipWith (+) coord d]

             successors _ = []                                                

         in [(pos, dir) | (pos, (dir, _)) <- directedPath successors isGoal start]