day 10 (ft. readme amendment. thanks day 10)

10-a.hs

@@ -0,0 +1,29 @@
+data Instruction = Add Int | Noop
+  deriving (Eq, Show)
+
+getCyclesAt = [20, 60 .. 220]
+
+parseInstruction :: String -> Instruction
+parseInstruction s = case head split of
+  "addx" -> Add (read $ split !! 1)
+  "noop" -> Noop
+  instr -> error $ "unknown instruction " ++ instr
+  where split = words s
+
+parse :: String -> [Instruction]
+parse = map parseInstruction . lines
+
+executeProgram :: [Instruction] -> [Int]
+executeProgram = concat . scanl exec [1]
+  where exec :: [Int] -> Instruction -> [Int]
+        exec xs instr = case instr of
+          (Add y) -> [x, x + y]
+          Noop -> [x]
+          where x = last xs
+
+main = interact $
+  show
+  . sum
+  . (\cycles -> map (\i -> i * cycles !! (i-1)) getCyclesAt)
+  . executeProgram
+  . parse

10-b.hs

@@ -0,0 +1,39 @@
+import GHC.Utils.Misc (chunkList)
+
+data Instruction = Add Int | Noop
+  deriving (Eq, Show)
+
+crtWidth = 40
+crtHeight = 6
+
+parseInstruction :: String -> Instruction
+parseInstruction s = case head split of
+  "addx" -> Add (read $ split !! 1)
+  "noop" -> Noop
+  instr -> error $ "unknown instruction " ++ instr
+  where split = words s
+
+parse :: String -> [Instruction]
+parse = map parseInstruction . lines
+
+executeProgram :: [Instruction] -> [Int]
+executeProgram = concat . scanl exec [1]
+  where exec :: [Int] -> Instruction -> [Int]
+        exec xs instr = case instr of
+          (Add y) -> [x, x + y]
+          Noop -> [x]
+          where x = last xs
+
+drawScreen :: [Int] -> String
+drawScreen cycles = unlines $ chunkList crtWidth $ map drawChar [0 .. (crtWidth * crtHeight - 1)]
+  where drawChar :: Int -> Char
+        drawChar i = if xDist <= 1 then '#' else '.'
+          where xScan = i `mod` crtWidth
+                xSprite = cycles !! (i)
+                xDist = abs (xScan - xSprite)
+
+main = interact $
+  (++ "\ni hope it is understandable for this to be an exception to the \"program must output something that's copypastable into aoc's output field\" rule that i've set for myself. read!!!!\n")
+  . drawScreen
+  . executeProgram
+  . parse

README.md

@@ -10,4 +10,4 @@ you shouldn't; but for documentation purposes it's
 $ ghc 1-a.hs && cat 1_input | ./1-a
 ```
 
-you'll need to retrieve `1_input` from your aoc, but all programs will strictly take in the aoc input and output what can be pasted into the anwser field
+you'll need to retrieve `1_input` from your aoc, but all programs will strictly take in the aoc input and ~~output what can be pasted into the anwser field~~ (thanks, day 10 part 2!)