Day6 and let identifiers contain ?

aoc2023/Aoc.newt

@@ -0,0 +1,19 @@
+module Aoc
+
+import Prelude
+
+nums : String → List Int
+nums s = map stringToInt $ filter (_/=_ "") $ split (trim s) " "
+
+isDigit : Char -> Bool
+isDigit '0' = True
+isDigit '1' = True
+isDigit '2' = True
+isDigit '3' = True
+isDigit '4' = True
+isDigit '5' = True
+isDigit '6' = True
+isDigit '7' = True
+isDigit '8' = True
+isDigit '9' = True
+isDigit _ = False

aoc2023/Day3.newt

@@ -2,6 +2,7 @@ module Day3
 
 import Prelude
 import Node
+import Aoc
 
 pfunc repr : {a : U} -> a -> String := `(a,o) => ''+o`
 pfunc jrepr : {a : U} -> a -> String := `(a,o) => JSON.stringify(o, null, '  ')`
@@ -15,18 +16,6 @@ maybe def f (Just a) = f a
 data Number : U where
   MkNumber : (start : Nat) -> (stop : Nat) → (value : Int) → Number
 
-isDigit : Char -> Bool
-isDigit '0' = True
-isDigit '1' = True
-isDigit '2' = True
-isDigit '3' = True
-isDigit '4' = True
-isDigit '5' = True
-isDigit '6' = True
-isDigit '7' = True
-isDigit '8' = True
-isDigit '9' = True
-isDigit _ = False
 
 numbers : List Char -> List Number
 numbers arr = go arr Z

aoc2023/Day6.newt

@@ -0,0 +1,74 @@
+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"

aoc2023/Prelude.newt

@@ -187,10 +187,13 @@ infixl 7 _+_
 class Add a where
   _+_ : a → a → a
 
-infixl 8 _*_
+infixl 8 _*_ _/_
 class Mul a where
   _*_ : a → a → a
 
+class Div a where
+  _/_ : a → a → a
+
 instance Add Nat where
   Z + m = m
   S n + m = S (n + m)
@@ -535,3 +538,29 @@ elem v (x :: xs) = if v == x then True else elem v xs
 -- sum : ∀ a. {{Add a}} → List a → a
 -- sum xs = foldl _+_
 pfunc trace uses (debugStr) : ∀ a. String -> a -> a := `(_, msg, a) => { console.log(msg,debugStr(_,a)); return a }`
+
+mapMaybe : ∀ a b. (a → Maybe b) → List a → List b
+mapMaybe f Nil = Nil
+mapMaybe f (x :: xs) = case f x of
+  Just y => y :: mapMaybe f xs
+  Nothing => mapMaybe f xs
+
+zip : ∀ a b. List a → List b → List (a × b)
+zip (x :: xs) (y :: ys) = (x,y) :: zip xs ys
+zip _ _ = Nil
+
+-- TODO add double literals
+ptype Double
+pfunc intToDouble : Int → Double := `(x) => x`
+pfunc doubleToInt : Double → Int := `(x) => x`
+pfunc addDouble : Double → Double → Double := `(x,y) => x + y`
+pfunc subDouble : Double → Double → Double := `(x,y) => x - y`
+pfunc mulDouble : Double → Double → Double := `(x,y) => x * y`
+pfunc divDouble : Double → Double → Double := `(x,y) => x / y`
+pfunc sqrtDouble : Double → Double := `(x) => Math.sqrt(x)`
+pfunc ceilDouble : Double → Double := `(x) => Math.ceil(x)`
+
+instance Add Double where x + y = addDouble x y
+instance Sub Double where x - y = subDouble x y
+instance Mul Double where x * y = mulDouble x y
+instance Div Double where x / y = divDouble x y

aoc2023/day6/eg.txt

@@ -0,0 +1,2 @@
+Time:      7  15   30
+Distance:  9  40  200