Part 1

day12/main.hs

@@ -9,7 +9,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE DeriveAnyClass #-}
 
-import Debug.Trace (trace)
+import Debug.Trace (trace, traceShowId, traceShow)
 import Text.Pretty.Simple
 import Control.Monad
 import Linear.V2
@@ -26,7 +26,7 @@ exampleData =
 
 
 
-data Ship = Ship { position :: V2 Int, orientation :: V2 Double }
+data Ship = Ship { position :: V2 Double, orientation :: V2 Double }
   deriving (Show, Eq, Ord)
 
 -- At first, ship is at (0,0) facing East
@@ -42,43 +42,51 @@ ship0 = Ship (pure 0) (V2 1 0)
 --   where
 --     mempty = Ship (pure 0) (pure 0)
 
-data Instruction  = InsMoveForward !Int
+data Instruction  = InsMoveForward !Double
-                  | InsMoveNorth !Int
+                  | InsMoveNorth !Double
-                  | InsMoveSouth !Int
+                  | InsMoveSouth !Double
-                  | InsMoveEast !Int
+                  | InsMoveEast !Double
-                  | InsMoveWest !Int
+                  | InsMoveWest !Double
-                  | InsTurnL !Int
+                  | InsTurnL !Double
-                  | InsTurnR !Int
+                  | InsTurnR !Double
   deriving (Show, Eq, Ord)
 
 parseIns :: String -> Instruction
 -- Action N means to move north by the given value.
-parseIns ('N':x) = InsMoveNorth (read x :: Int)
+parseIns ('N':x) = InsMoveNorth (read x)
 -- Action S means to move south by the given value.
-parseIns ('S':x) = InsMoveSouth (read x :: Int)
+parseIns ('S':x) = InsMoveSouth (read x)
 -- Action E means to move east by the given value.
-parseIns ('E':x) = InsMoveEast (read x :: Int)
+parseIns ('E':x) = InsMoveEast (read x)
 -- Action W means to move west by the given value.
-parseIns ('W':x) = InsMoveWest (read x :: Int)
+parseIns ('W':x) = InsMoveWest (read x)
 -- Action L means to turn left the given number of degrees.
-parseIns ('L':x) = InsTurnL (read x :: Int)
+parseIns ('L':x) = InsTurnL (read x)
 -- Action R means to turn right the given number of degrees.
-parseIns ('R':x) = InsTurnR (read x :: Int)
+parseIns ('R':x) = InsTurnR (read x)
 -- Action F means to move forward by the given value in the direction the ship is currently facing.
-parseIns ('F':x) = InsMoveForward (read x :: Int)
+parseIns ('F':x) = InsMoveForward (read x)
 parseIns e = trace ("Unknown instruction: "<>show e) undefined
 
-runIns :: Instruction -> Ship -> Ship
-runIns (InsMoveForward n) s = s { position = (position s) + fmap truncate ((pure $ fromIntegral n) * (orientation s)) }
-runIns (InsMoveNorth n)   s = s { position = (position s) + (pure n) * V2 0     (-1) }
-runIns (InsMoveSouth n)   s = s { position = (position s) + (pure n) * V2 0     1    }
-runIns (InsMoveEast n)    s = s { position = (position s) + (pure n) * V2 1     0    }
-runIns (InsMoveWest n)    s = s { position = (position s) + (pure n) * V2 (-1)  0    }
-runIns (InsTurnL n)       s = s { orientation = (orientation s) + angle (fromIntegral n :: Double) }
-runIns (InsTurnR n)       s = s { orientation = (orientation s) - angle (fromIntegral n :: Double) }
 
-solvePart1 :: [String] -> Ship
+-- 2*PI rad = 360 deg
-solvePart1 = foldr runIns ship0 . map parseIns
+-- 1 rad = 180/PI deg
+-- PI/180 rad = 1 deg
+
+runIns :: Ship -> Instruction -> Ship
+runIns s (InsMoveForward n) = s { position = (position s) + (pure n) * (orientation s) }
+runIns s (InsMoveNorth n)   = s { position = (position s) + (pure n) * V2 0     1    }
+runIns s (InsMoveSouth n)   = s { position = (position s) + (pure n) * V2 0     (-1) }
+runIns s (InsMoveEast n)    = s { position = (position s) + (pure n) * V2 1     0    }
+runIns s (InsMoveWest n)    = s { position = (position s) + (pure n) * V2 (-1)  0    }
+runIns s (InsTurnL n)       = s { orientation = angle ((unangle (orientation s)) + n * pi / 180) }
+runIns s (InsTurnR n)       = s { orientation = angle ((unangle (orientation s)) - n * pi / 180) }
+
+manhattanV2 :: (Num a) => V2 a -> a
+manhattanV2 (V2 x y) = (abs x) + (abs y)
+
+solvePart1 :: [String] -> Double
+solvePart1 = manhattanV2 . position . foldl runIns ship0 . map parseIns
 
 main :: IO ()
 main = do
@@ -86,5 +94,7 @@ main = do
   putStrLn ":: Tests"
   pPrint exampleData
   pPrint $ map parseIns exampleData
+  pPrint $ angle (90 * pi / 180)
   putStrLn ":: Day 12 - Part 1"
   pPrint $ solvePart1 exampleData
+  pPrint $ solvePart1 input