Day 2

app/Main.hs

@@ -1,17 +1,36 @@
 module Main where
 
 import Day1
+import Day2
 import System.IO
-
+import Data.List.Split
 
 day1_fuel :: String -> [Fuel]
 day1_fuel = fmap (calculateFuel . read) . lines
 
+day2_instructions :: String -> [Integer]
+day2_instructions = fmap read . splitOn ","
+
+day2 :: (Integer, Integer) -> [Integer] -> Integer
+day2 t = head . execute t
+
+day2_look :: [Integer] -> Integer
+day2_look xs = head $ [ 100*noun + verb |
+                        noun <- [0..99],
+                        verb <- [0..99],
+                        day2 (noun, verb) xs == 19690720 ]
+
 main :: IO ()
 main = do
-    r <- readFile "./app/input_day1"
+    r_day1 <- readFile "./app/input_day1"
     putStr "[Day 1-1] Fuel needed: "
-    let fs = day1_fuel r
+    let fs = day1_fuel r_day1
     print $ sum fs
     putStr "[Day 1-2] Fuel needed: "
     print (sum fs + (sum . fmap calculateFuelOfFuel) fs)
+    r_day2 <- readFile "./app/input_day2"
+    let instructions = day2_instructions r_day2
+    putStr "[Day 2-1] Result:"
+    print $ day2 (12,2) instructions
+    putStr "[Day 2-2] Result:"
+    print $ day2_look instructions

app/input_day2

@@ -0,0 +1 @@
+1,0,0,3,1,1,2,3,1,3,4,3,1,5,0,3,2,1,13,19,1,9,19,23,2,13,23,27,2,27,13,31,2,31,10,35,1,6,35,39,1,5,39,43,1,10,43,47,1,5,47,51,1,13,51,55,2,55,9,59,1,6,59,63,1,13,63,67,1,6,67,71,1,71,10,75,2,13,75,79,1,5,79,83,2,83,6,87,1,6,87,91,1,91,13,95,1,95,13,99,2,99,13,103,1,103,5,107,2,107,10,111,1,5,111,115,1,2,115,119,1,119,6,0,99,2,0,14,0

package.yaml

@@ -21,6 +21,8 @@ description:         Please see the README on GitHub at <https://github.com/gith
 
 dependencies:
 - base >= 4.7 && < 5
+- containers >= 0.6
+- split >= 0.1
 
 library:
   source-dirs: src

src/Day2.hs

@@ -0,0 +1,40 @@
+module Day2
+    (
+        execute
+    ) where
+
+import Data.Sequence
+import Data.Foldable
+import Control.Applicative
+
+preRun :: (Integer, Integer) -> Seq Integer -> Seq Integer
+preRun (noun, verb) = update 1 noun . update 2 verb
+
+execute :: (Integer, Integer) -> [Integer] -> [Integer]
+execute t = toList . executeCommandAtIndex 0 . preRun t . fromList
+
+executeCommandAtIndex :: Int -> Seq Integer -> Seq Integer
+executeCommandAtIndex i xs =
+    case (!?) xs i of
+        Just 1 -> executeCommandAtIndex (i + 4) (executeAddCommand i xs)
+        Just 2 -> executeCommandAtIndex (i + 4) (executeMulCommand i xs)
+        Just 99 -> xs
+        _ -> error "Unknown Command"
+
+executeAddCommand :: Int -> Seq Integer -> Seq Integer
+executeAddCommand = executeCommand (+)
+
+executeMulCommand :: Int -> Seq Integer -> Seq Integer
+executeMulCommand = executeCommand (*)
+
+executeCommand ::
+    (Integer -> Integer -> Integer) -> Int -> Seq Integer -> Seq Integer
+executeCommand f i xs = update n v xs
+    where t1 = (!?) xs (i+1) >>= (!?) xs . fromIntegral
+          t2 = (!?) xs (i+2) >>= (!?) xs . fromIntegral
+          n = case (!?) xs (i+3) of
+              Just n' -> fromIntegral n'
+              _ -> error "Can't find update index"
+          v = case liftA2 f t1 t2 of
+              Just v' -> v'
+              _ -> error "blah"