Day6 and let identifiers contain ?

aoc2023/Day6.newt

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+module Day6
+
+import Prelude
+import Node
+import Aoc
+
+Problem : U
+Problem = List (Int × Int)
+
+pNums : String → Either String (List Int)
+pNums line =
+  let (_ :: line :: Nil) = split line ": "
+    | _ => Left "expected two parts" in
+  Right $ nums line
+
+parse : String → Either String Problem
+parse content = do
+  let (a :: b :: Nil) = split (trim content) "\n"
+    | _ => Left "expected two lines"
+  times <- pNums a
+  dists <- pNums b
+  Right (zip times dists)
+
+part1 : Problem → Int
+part1 prob = go 1 prob
+  where
+    run : Int -> Int -> Int → Int → Int
+    run time dist t count =
+      let count = if dist < t * (time - t) then count + 1 else count in
+      if time == t then count
+      else run time dist (t + 1) count
+
+    go : Int → Problem → Int
+    go acc Nil = acc
+    go acc ((time,dist) :: prob) = go (acc * run time dist 0 0) prob
+
+part2 : Int × Int → IO Unit
+part2 (time,dist) = do
+  let t = intToDouble time
+  let d = intToDouble dist
+  let x = sqrtDouble (t * t - intToDouble 4 * d)
+  let start = (t - x) / intToDouble 2
+  let stop = (t + x) / intToDouble 2
+  let s = doubleToInt $ ceilDouble start
+  let e = doubleToInt $ ceilDouble stop
+  putStrLn $ "part2 " ++ show (e - s)
+
+parse2 : String → Either String (Int × Int)
+parse2 content =
+  let (a :: b :: Nil) = split (trim content) "\n"
+    | _ => Left "too many parts" in
+  let time = stringToInt $ pack $ filter isDigit $ unpack a
+      dist = stringToInt $ pack $ filter isDigit $ unpack b
+  in Right (time, dist)
+
+run : String -> IO Unit
+run fn = do
+  putStrLn fn
+  text <- readFile fn
+  let (Right prob) = parse text | Left err => putStrLn err
+  putStrLn $ debugStr prob
+  putStrLn $ "part1 " ++ show (part1 prob)
+  let (Right prob) = parse2 text | Left err => putStrLn err
+  part2 prob
+  -- debugLog prob
+  -- part2 prob
+
+-- 288 / 71503
+-- 1413720 / 30565288
+
+main : IO Unit
+main = do
+  run "aoc2023/day6/eg.txt"
+  run "aoc2023/day6/input.txt"