Two stars on day 2 as well!

2022/aoc2022.cabal

@@ -32,4 +32,4 @@ executable aoc2022
     build-depends:    base ^>=4.16.3.0
     hs-source-dirs:   app
     default-language: Haskell2010
-    other-modules:    Day1.Main
+    other-modules:    Day1.Main Day2.Main

2022/app/Day2/Main.hs

@@ -0,0 +1,89 @@
+module Day2.Main (main) where
+
+import Data.List
+import Data.Tuple
+import Data.Maybe
+import System.IO
+import Control.Monad
+
+main :: IO ()
+main = do
+    putStrLn "Day 2"
+    
+    handle <- openFile "app/Day2/input" ReadMode
+    contents <- hGetContents handle
+
+    let r1 = part1 contents
+    putStrLn $ "part 1: " ++ show r1
+
+    let r2 = part2 contents
+    putStrLn $ "part 2: " ++ show r2
+
+data Shape = Rock | Paper | Scissors
+             deriving (Show, Eq)
+
+instance Read Shape where
+    readsPrec _ "A" = [(Rock,     "")]
+    readsPrec _ "B" = [(Paper,    "")]
+    readsPrec _ "C" = [(Scissors, "")]
+    
+    readsPrec _ "X" = [(Rock,     "")]
+    readsPrec _ "Y" = [(Paper,    "")]
+    readsPrec _ "Z" = [(Scissors, "")]
+
+    readsPrec _ _   = []
+
+instance Enum Shape where
+    fromEnum Rock     = 1
+    fromEnum Paper    = 2
+    fromEnum Scissors = 3
+
+    toEnum _ = error "nope"
+
+data Result = Loss | Tie | Win
+              deriving (Show, Eq)
+
+instance Read Result where
+    readsPrec _ "X" = [(Loss, "")]
+    readsPrec _ "Y" = [(Tie,  "")]
+    readsPrec _ "Z" = [(Win,  "")]
+    readsPrec _ _   = []
+
+instance Enum Result where
+    fromEnum Loss = 0
+    fromEnum Tie  = 3
+    fromEnum Win  = 6
+
+    toEnum _ = error "nope"
+
+result :: Shape -> Shape -> Result
+result a b | a == b   = Tie
+result Rock Paper     = Loss
+result Rock Scissors  = Win
+result Paper Rock     = Win
+result Paper Scissors = Loss
+result Scissors Rock  = Loss
+result Scissors Paper = Win
+
+parseInput :: String -> (String -> a) -> (String -> b) -> [(a, b)]
+parseInput contents lhs rhs = shapes
+    where
+        rounds = lines contents
+        picks = map (\l -> ([l !! 0], [l !! 2])) rounds
+        shapes = map (\(a,b) -> (lhs a, rhs b)) picks
+
+part1 :: String -> Int
+part1 contents = sum scoresResults + sum scoresPicks
+    where
+        rounds = parseInput contents (read :: String -> Shape) (read :: String -> Shape)
+        scoresResults = map (fromEnum . (uncurry result) . swap) rounds
+        scoresPicks = map (fromEnum . snd) rounds
+
+part2 :: String -> Int
+part2 contents = sum solutions + sum outcomes
+    where
+        rounds = parseInput contents (read :: String -> Shape) (read :: String -> Result)
+        getResult o r = fromJust $ find (\p -> result p o == r) [Rock,Paper,Scissors]
+        solutions = map (fromEnum . uncurry getResult) rounds
+        outcomes = map (fromEnum . snd) rounds
+        

2022/app/Main.hs

@@ -1,7 +1,9 @@
 module Main where
 
 import qualified Day1.Main as Day1
+import qualified Day2.Main as Day2
 
 main :: IO ()
 main = do
     Day1.main
+    Day2.main