PhisicalCell データ型の単純な show インスタンスを手動で作成すると、プログラムがすべてのスペースを消費します。彼自身のバージョンの Show を導出するとき、これは起こりません。なんで?
ここに私が書いているコードの簡素化されたバージョンがあります:
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) [])