Advent of Code 2019

day1.hs

module Main where  

elfFuel :: Int -> Int  
elfFuel mass = mass `div` 3 - 2  

cumulativeElfFuel :: Int -> Int  
cumulativeElfFuel mass
  | elfFuel mass <= 0 = 0  
  | mass > 0 = (elfFuel mass) + cumulativeElfFuel (elfFuel mass)

appliedSum :: Num c => (a -> c) -> [a] -> c
appliedSum f vs = sum $ map f vs

intFromLine :: Read b => (b -> Int) -> String -> Int
intFromLine v = (v . read :: String -> Int)

part1 :: [String] -> Int
part1 masses = appliedSum (intFromLine $ elfFuel) $ masses

part2 :: [String] -> Int
part2 masses = appliedSum (intFromLine $ cumulativeElfFuel) $ masses

main = do  
  input <- readFile "input"  
  let masses = lines input

  print (part1 masses)
  print (part2 masses)