Day 2

Day2.hs

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+{-# LANGUAGE OverloadedStrings #-}
+
+module Day2 where
+
+import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
+import Data.Text (splitOn, Text, unpack, pack)
+
+
+data Submarine = Submarine {
+        horizontal :: Int
+    ,   depth      :: Int
+    } deriving Show
+
+type Movement = (String, Int)
+
+-- "forward 5" -> ("forward", 5)
+parseInstruction :: String -> Movement
+parseInstruction instr = (kind, magnitude)
+    where
+        split = map unpack $ splitOn " " $ pack instr
+        kind = head split
+        magnitude = read $ split !! 1
+
+move :: Submarine -> Movement -> Submarine
+move sub ("forward", magnitude) = sub { horizontal = horizontal sub + magnitude }
+move sub ("down", magnitude)    = sub { depth = depth sub + magnitude }
+move sub ("up", magnitude)      = sub { depth = depth sub - magnitude }
+
+(++) :: Submarine -> Submarine -> Submarine
+x ++ y = Submarine { horizontal = horizontal x + horizontal y, depth = depth x + depth y } 
+
+main :: IO ()
+main = do
+    input <- openFile "inputs/2.txt" ReadMode 
+    contents <- hGetContents input
+
+    let submarine = Submarine { horizontal = 0, depth = 0 }
+    let instructions = parseInstruction <$> lines contents
+    let sub = foldl move submarine instructions
+
+    print $ horizontal sub * depth sub
+
+    hClose input

Day2_1.hs

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+{-# LANGUAGE OverloadedStrings #-}
+
+module Day2_1 where
+
+import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
+import Data.Text (splitOn, Text, unpack, pack)
+import Data.List (mapAccumL)
+import Prelude hiding ((++))
+
+
+data Submarine = Submarine {
+        horizontal :: Int
+    ,   depth      :: Int
+    ,   aim        :: Int
+    } deriving Show
+
+type Movement = (String, Int)
+
+-- "forward 5" -> ("forward", 5)
+parseInstruction :: String -> Movement
+parseInstruction instr = (kind, magnitude)
+    where
+        split = map unpack $ splitOn " " $ pack instr
+        kind = head split
+        magnitude = read $ split !! 1
+
+move :: Submarine -> Movement -> Submarine
+move sub ("forward", magnitude) = sub { depth = depth sub + (aim sub * magnitude), horizontal = horizontal sub + magnitude }
+move sub ("down", magnitude)    = sub { aim = aim sub + magnitude }
+move sub ("up", magnitude)      = sub { aim = aim sub - magnitude }
+
+main :: IO ()
+main = do
+    input <- openFile "inputs/2.txt" ReadMode
+    contents <- hGetContents input
+
+    let submarine = Submarine { horizontal = 0, depth = 0, aim = 0 }
+    let instructions = parseInstruction <$> lines contents
+    let sub = foldl move submarine instructions
+
+    print $ horizontal sub * depth sub
+
+    hClose input