Internal/Karel.hs

@@ -15,6 +15,10 @@ data Karel = Karel
   }
   deriving (Eq)
 
+xor :: Bool -> Bool -> Bool
+xor True a = not a
+xor False a = a
+
 getHeader :: Karel -> String
 getHeader karel = unlines [
     printf " %8s   %s  %s  %s" "POSITION" "FACING" "BEEP-BAG" "BEEP-POS",
@@ -50,32 +54,27 @@ mapCell karel x y
   | otherwise = " . "
   where beepersAt = getBeepersAt (x, y) $ karelWorld karel
 
+
 mapWall :: Karel -> Int -> Int -> String
 mapWall karel x y = leftPart <> rightPart
   where
     world = karelWorld karel
-    (width, height) = worldDimensions world
-    wallAtNorth = hasWallAt (x, y) North world
-    vWallAbove = hasWallAt (x, y + 1) East world
-    vWallBelow = hasWallAt (x, y - 1) East world
-    vWallAt = hasWallAt (x, y) East world
-    verticalWall = vWallAt && vWallAbove
-    wallEnds = wallAtNorth && (not $ hasWallAt (x + 1, y) North world)
-    wallStarts = wallAtNorth && x > 1 && (not $ hasWallAt (x - 1, y) North world)
-    noVWall = not (hasWallAt (x, y) West world || hasWallAt (x, y + 1) West world)
+    (northWall:eastWall:westWall:_) = map (\d -> hasWallAt (x, y) d world) [North, East, West]
+    (northWallOnLeft:northWallOnRight:_) = map (\d -> hasWallAt (x + d, y) North world) [-1, 1]
+    (eastWallAbove:westWallAbove:_) = map (\d -> hasWallAt (x, y + 1) d world) [East, West]
+    verticalWall = eastWall && eastWallAbove
+    wallEnds = northWall && not northWallOnRight
+    wallStarts = northWall && x > 1 && not northWallOnLeft
     leftPart
-      | wallStarts && noVWall = "+-"
-      | wallAtNorth = "--"
+      | wallStarts && not (westWall || westWallAbove) = "+-"
+      | northWall = "--"
       | otherwise = "  "
     rightPart
-      | wallAtNorth && wallEnds && verticalWall = "-|"
-      | wallEnds = "-+"
-      | wallAtNorth && (vWallAbove) = "-+"
-      | wallAtNorth = "--"
-      | verticalWall && hasWallAt (x+1, y) North world = " +"
+      | northWall && wallEnds && verticalWall = "-|"
+      | wallEnds || (northWall && eastWallAbove) = "-+"
+      | northWall = "--"
+      | (verticalWall && northWallOnRight) || (eastWall `xor` eastWallAbove) = " +"
       | verticalWall = " |"
-      | not vWallAbove && vWallAt = " +"
-      | not vWallAt && vWallAbove = " +"
       | otherwise = "  "
 
 getRow :: Karel -> Int -> String
@@ -89,7 +88,7 @@ getRow karel row
       mapWall karel column row
       | column <- [1..width]
       ]
-    line = (printf "%2d |" row) <> foldl1 (<>) [
+    line = printf "%2d |" row <> foldl1 (<>) [
       position <> wall
       | column <- [1..width],
       let wall = if hasWallAt (column, row) East world then "|" else " ",