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POA tricky haskell problem
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copied!<p>I had this task for my Haskell class, but I find it quite difficult. If you could help a bit. You are given a maze </p> <pre><code>maze = ["x xxx", "x x", "x x x", "x x ", "xxxxx"] </code></pre> <p>and you can walk through spaces only . You start from (0,1) and the function have to return a string with directions to escape the maze which are :</p> <pre><code>f - forward r- turn right l - turn left </code></pre> <p>And if you have a choice you always prefer right to forward, and forward to left. For the current example the answer is <code>ffllffrffrfflf</code></p> <p>Thanks in advance</p> <pre><code>data Direction = N | W | S | E deriving (Show,Eq) maze = ["x xxx", "x x", "x x x", "x x ", "xxxxx"] d = 's' pos = (0,1) fpath d pos | fst pos == (length maze - 1) = "" | snd (pos) ==0 || (snd ( pos ) == ((length (maze!!0))-1)) = "" | rightPossible d pos = "r" ++ ( fpath (rightRotate d) pos ) | forwardPossible d pos = "f" ++ ( fpath d (nstep d pos) ) | True = "l" ++ fpath (leftRotate d) pos where nstep :: Direction -> (Int, Int) -> (Int, Int) {-next step-} nstep N (x,y) = (x-1,y) nstep W (x,y) = (x,y-1) nstep S (x,y) = (x+1,y) nstep E (x,y) = (x,y+1) rightPossible :: Direction -> (Int, Int) -> Bool rightPossible N (x,y)= (maze !! x)!! (y+1) == ' ' rightPossible W (x,y)= (maze !! (x-1))!! y == ' ' rightPossible S (x,y)= (maze !! x)!! (y-1) == ' ' rightPossible E (x,y)= (maze !! (x+1))!! y == ' ' rightRotate :: Direction -> Direction rightRotate N = E rightRotate W = N rightRotate S = W rightRotate E = S forwardPossible :: Direction -> (Int, Int) -> Bool forwardPossible N (x,y)= ((maze !! (x-1))!! y) == ' ' forwardPossible W (x,y)= ((maze !! x)!! (y-1)) == ' ' forwardPossible S (x,y)= ((maze !! (x+1))!! y) == ' ' forwardPossible E (x,y)= ((maze !! x)!! (y+1)) == ' ' leftRotate :: Direction -> Direction leftRotate N = W leftRotate W = S leftRotate S = E leftRotate E = N </code></pre>

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