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POmanual Instance Show definition causes Stack Space Overflow
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copied!<p>When I write manually a simple show instance for the PhisicalCell datatype, the program consumes all the space. When deriving his own version of Show, this doesn't happen. Why?</p> <p>here is a stripped-down version of the code I'm writing:</p> <pre><code>import Data.Array type Dimensions = (Int, Int) type Position = (Int, Int) data PipeType = Vertical | Horizontal | UpLeft | UpRight | DownLeft | DownRight deriving (Show) data PhisicalCell = AirCell | PipeCell PipeType | DeathCell | RecipientCell Object -- deriving (Show) SEE THE PROBLEM BELOW data Object = Pipe { pipeType :: PipeType -- tipo di tubo , position :: Position -- posizione del tubo , movable :: Bool -- se posso muoverlo } | Bowl { position :: Position -- posizione dell'angolo in alto a sinistra , dimensions :: Dimensions -- dimensioni (orizzontale, verticale) , waterMax :: Int -- quanta acqua puo' contenere al massimo , waterStart :: Int -- con quanta acqua parte , hatch :: Maybe Position -- un eventuale casella di sbocco , sourceIn :: [Position] -- posti da cui l'acqua entra , movable :: Bool -- se posso muoverlo } | Death deriving (Show) data Level = Level Dimensions [Object] type LevelTable = Array Dimensions PhisicalCell -- HERE IS THE PROBLEM -- instance Show PhisicalCell where show AirCell = " " show (PipeCell _) = "P" show DeathCell = "X" show (RecipientCell _) = "U" both :: (a -> b) -> (a,a) -> (b,b) both f (a,b) = (f a, f b) levelTable :: Level -> LevelTable levelTable (Level dim _) = initial where initial = array ((0,0), both (+1) dim) $ [((x,y), AirCell) | x <- [1..fst dim], y <- [1..snd dim] ] ++ [((x,y), DeathCell) | x <- [0..fst dim + 1], y <- [0, snd dim + 1]] ++ [((x,y), DeathCell) | x <- [0, fst dim + 1], y <- [0..snd dim + 1]] main = print $ levelTable (Level (8,12) []) </code></pre>

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