advent18/src/advent18.hs

   1 -- import Debug.Trace
   2
   3 import Data.Text (Text)
   4 -- import qualified Data.Text as T
   5 import qualified Data.Text.IO as TIO
   6
   7 import Data.Attoparsec.Text hiding (take)
   8 -- import Data.Attoparsec.Combinator
   9 import Control.Applicative
  10 -- import Control.Applicative.Combinators
  11
  12 data Expression
  13   = Number Integer
  14   | Mul Expression Expression
  15   | Add Expression Expression
  16   deriving (Show, Eq)
  17
  18
  19 main :: IO ()
  20 main =
  21   do  text <- TIO.readFile "data/advent18.txt"
  22       print $ part1 text
  23       print $ part2 text
  24
  25
  26 part1 = parseAndEval expressionsP
  27 part2 = parseAndEval pExpressionsP
  28
  29 parseAndEval parser text = sumEval $ successfulParse parser text
  30
  31 sumEval = sum . map evaluate
  32
  33 showE (Number x) = show x
  34 showE (Mul a b) = "(" ++ showE a ++ " * " ++ showE b ++ ")"
  35 showE (Add a b) = "(" ++ showE a ++ " + " ++ showE b ++ ")"
  36
  37 evaluate (Number x)  = x
  38 evaluate (Mul a b) = (evaluate a) * (evaluate b)
  39 evaluate (Add a b) = (evaluate a) + (evaluate b)
  40
  41
  42 -- Parse the input file
  43
  44 numberP = Number <$> decimal
  45 mulExprP = string " * " *> pure Mul
  46 addExprP = string " + " *> pure Add
  47
  48
  49 -- Part 1 parsing
  50
  51 expressionsP = exprP `sepBy` endOfLine
  52
  53 exprP = elementP `chainl1` (mulExprP <|> addExprP)
  54
  55 elementP = numberP <|> bracketedP
  56 bracketedP = "(" *> exprP <* ")"
  57
  58
  59 -- Part 2 parsing
  60
  61 pExpressionsP = pExprP `sepBy` endOfLine
  62
  63 pExprP = pTermP `chainl1` mulExprP
  64 pTermP = pElementP `chainl1` addExprP
  65
  66 pElementP = numberP <|> pBracketedP
  67 pBracketedP = "(" *> pExprP <* ")"
  68
  69
  70 -- chainl1 :: Parser a -> Parser (a -> a -> a) -> Parser a
  71 -- chainl1 p op = p >>= rest
  72 --     where
  73 --         rest a = (do
  74 --             f <- op
  75 --             b <- p
  76 --             rest (f a b)) <|> pure a
  77
  78
  79 chainl1 :: Parser a -> Parser (a -> a -> a) -> Parser a
  80 p `chainl1` op = do a <- p
  81                     rest a
  82   where rest a = (do f <- op
  83                      b <- p
  84                      rest (f a b))
  85                  <|> return a
  86
  87
  88 -- successfulParse :: Text -> (Integer, [Maybe Integer])
  89 successfulParse parser input =
  90   case parseOnly parser input of
  91     Left  _err -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err
  92     Right expressions -> expressions