Quest 4: Teeth of the Wind

I liked this one!

import Control.Arrow  
import Control.Monad  
import Data.List  
import Data.Ratio  

simpleTrain = uncurry (%) . (head &&& last) . map read  

compoundTrain input =  
  let a = read $ head input  
      z = read $ last input  
      gs =  
        map  
          ( uncurry (%)  
              . (read *** read . tail)  
              . break (== '|')  
          )  
          $ (tail . init) input  
   in foldl' (/) (a % z) gs  

part1, part2, part3 :: [String] -> Integer  
part1 = floor . (2025 *) . simpleTrain  
part2 = ceiling . (10000000000000 /) . simpleTrain  
part3 = floor . (100 *) . compoundTrain  

main =  
  forM_  
    [ ("everybody_codes_e2025_q04_p1.txt", part1),  
      ("everybody_codes_e2025_q04_p2.txt", part2),  
      ("everybody_codes_e2025_q04_p3.txt", part3)  
    ]  
    $ \(input, solve) -> readFile input >>= print . solve . lines