haskell: 2023 10 parser

2023/haskell/aoc2023.cabal

@@ -27,6 +27,7 @@ library
     Day07
     Day08
     Day09
+    Day10
 
   -- other-modules:
 

2023/haskell/solutions/Day10.hs

@@ -0,0 +1,52 @@
+{-# LANGUAGE OverloadedStrings #-}
+module Day10 where
+
+import Data.Void (Void)
+import Data.Text (Text)
+import Data.Char (isSpace)
+import Data.Bifunctor (first)
+import Text.Megaparsec (Parsec, errorBundlePretty, runParser, many, eof, satisfy)
+import Text.Megaparsec.Char (newline)
+
+
+data Pipe = E | S | UD | LR | UL | UR | DL | DR
+  deriving Show
+
+data Dir = L | R | U | D
+
+type Row = Int
+type Col = Int
+
+type Parser = Parsec Void Text
+
+
+input :: Text
+input =
+  ".....\n\
+  \.S-7.\n\
+  \.|.|.\n\
+  \.L-J.\n\
+  \.....\n"
+
+parse :: Text -> Either String [[Pipe]]
+parse = first errorBundlePretty . runParser grid ""
+  where
+    pipe :: Char -> Pipe
+    pipe c = case c of
+      '.' -> E
+      'S' -> S
+      '|' -> UD
+      '-' -> LR
+      'J' -> UL
+      'L' -> UR
+      '7' -> DL
+      'F' -> DR
+      bad -> error $ "Invalid character: " <> [bad]
+    row :: Parser [Pipe]
+    row = map pipe <$> many (satisfy $ not . isSpace) <* newline
+    grid :: Parser [[Pipe]]
+    grid = many row <* eof
+
+-- >>> parse input
+-- Right [[E,E,E,E,E],[E,S,LR,DL,E],[E,UD,E,UD,E],[E,UR,LR,UL,E],[E,E,E,E,E]]
+