76 lines
1.4 KiB
Haskell
76 lines
1.4 KiB
Haskell
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module Day7 where
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import Data.Char
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import Text.ParserCombinators.ReadP
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letter = satisfy isLetter
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space = satisfy isSpace
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digit = satisfy isDigit
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parse p s = parsedResult $ readP_to_S p s
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where
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parsedResult [(a, "")] = a
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parsedResult [(_, rs)] = error "Parser did not consume entire stream."
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parsedResult (a:as) = parsedResult as
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parsedResult _ = error "Parser error"
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data Bag = Bag { name :: String }
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deriving (Show)
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bagName :: ReadP String
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bagName = many1 (letter +++ space)
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bag :: ReadP Bag
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bag = do
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name' <- bagName
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_ <- space
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_ <- string "bags" <++ string "bag"
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return (Bag name')
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int :: ReadP Int
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int = do
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digits <- many1 digit
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return $ read digits
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data Numbered a = Numbered { item :: a, value :: Int }
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deriving (Show)
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numberedBag :: ReadP (Numbered Bag)
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numberedBag = do
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value' <- int
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_ <- space
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bag' <- bag
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return (Numbered bag' value')
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data Rule = Rule { container :: Bag, contents :: [Numbered Bag] }
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deriving (Show)
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noOtherBags :: ReadP [Numbered Bag]
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noOtherBags = do
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_ <- string "no other bags"
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return []
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comma :: ReadP String
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comma = string ", "
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rule :: ReadP Rule
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rule = do
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container' <- bag
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_ <- space
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_ <- string "contain"
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_ <- space
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contents' <- noOtherBags <++ (numberedBag `sepBy1` comma)
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return (Rule container' contents')
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period = char '.'
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endRule :: ReadP ()
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endRule = do
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_ <- period
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skipSpaces
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return ()
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rules :: ReadP [Rule]
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rules = rule `endBy1` endRule
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