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Diffstat (limited to '')
-rw-r--r-- | 2024/03-Mull_It_Over/first.hs | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/2024/03-Mull_It_Over/first.hs b/2024/03-Mull_It_Over/first.hs new file mode 100644 index 0000000..734ef85 --- /dev/null +++ b/2024/03-Mull_It_Over/first.hs @@ -0,0 +1,45 @@ +-- requires cabal install --lib megaparsec parser-combinators heap vector +module Main (main) where + +import Control.Monad (void, when) +import Data.Functor +import Data.Maybe +import Data.Void (Void) +import Text.Megaparsec +import Text.Megaparsec.Char + +exampleExpectedOutput = 161 + +data Mul = Mul Int Int +type Input = [Mul] + +type Parser = Parsec Void String + +parseNumber :: Parser Int +parseNumber = read <$> some digitChar + +parseMul :: Parser (Maybe Mul) +parseMul = try (Just <$> (Mul <$> (string "mul(" *> parseNumber) + <*> (char ',' *> parseNumber <* char ')'))) + <|> anySingle $> Nothing + +parseInput' :: Parser Input +parseInput' = catMaybes <$> some parseMul <* eof + +parseInput :: String -> IO Input +parseInput filename = do + input <- readFile filename + case runParser parseInput' filename input of + Left bundle -> error $ errorBundlePretty bundle + Right input' -> return input' + +compute :: Input -> Int +compute = sum . map (\(Mul x y) -> x * y) + +main :: IO () +main = do + example <- parseInput "example" + let exampleOutput = compute example + when (exampleOutput /= exampleExpectedOutput) (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput) + input <- parseInput "input" + print $ compute input |