2023.01.1 in Haskell

challenges/2023/01-trebuchet/README.md

@@ -1 +1,3 @@
 # [Day 1: Trebuchet?!](https://adventofcode.com/2023/day/1)
+
+The Haskell implementation included here is only partial, mostly because I ran out of patience with it after taking an age to implement the CLI required.

challenges/2023/01-trebuchet/main.hs

@@ -0,0 +1,42 @@
+import System.Environment
+import System.Exit
+import System.IO
+import Data.Maybe
+import Data.Char
+import Control.Exception
+
+type ChallengeReturn = Int
+
+parse :: String -> [String]
+parse = lines
+
+one :: String -> ChallengeReturn
+one inp = foldl
+    (\acc line ->
+        let digits = map (\x -> ord x - ord '0') (filter isDigit line) in
+            assert ((length digits) /= 0) (
+                acc + ((digits!!0) * 10) + (digits!!((length digits) - 1))
+            )
+    )
+    0
+    (parse inp)
+
+two :: String -> ChallengeReturn
+two inp = undefined
+
+main :: IO ()
+main = do args <- getArgs
+          inp <- getContents
+          _runFn (_selectFn args) inp
+
+_selectFn :: [String] -> Maybe (String -> ChallengeReturn)
+_selectFn ["1"] = Just one
+_selectFn ["2"] = Just two
+_selectFn _ = Nothing
+
+_runFn :: Maybe (String -> ChallengeReturn) -> String -> IO ()
+_runFn Nothing _ = _debug "Missing or invalid day argument" >> exitWith (ExitFailure 1)
+_runFn (Just fn) inp = putStrLn (show (fn inp)) >> exitWith ExitSuccess
+
+_debug :: String -> IO ()
+_debug x = do hPutStrLn stderr x