Day 23

day23/Commons.hs

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+module Commons where
+
+import GHC.IO.Handle (isEOF)
+import Data.Array (Array, listArray, (!), Ix (inRange), bounds)
+
+
+data Direction = North | South | West | East deriving (Eq, Ord, Show)
+data Tile = Empty | Rock | Slope { direction :: Direction } deriving (Eq, Show)
+type Trails = Array (Int, Int) Tile
+
+
+parseLine :: String -> [Tile]
+parseLine = map (\case
+                  '.' -> Empty
+                  '#' -> Rock
+                  '>' -> Slope {direction = East}
+                  'v' -> Slope {direction = South}
+                  '<' -> Slope {direction = West}
+                  '^' -> Slope {direction = North})
+
+parseTrails :: IO [[Tile]]
+parseTrails = do done <- isEOF
+                 if done
+                    then return []
+                    else do line <- getLine
+                            let trailsLine = parseLine line
+                            trails <- parseTrails
+                            return (trailsLine: trails)
+
+parse :: IO Trails
+parse = do trails <- parseTrails
+           return $ listArray ((1, 1), (length trails, length $ head trails)) $ concat trails