Merge multiple user inputs during same tick

Author: qxjit

src/Life.hs

@@ -5,11 +5,13 @@ module Life
   , World
   , newWorld
   , newWorldWithCells
+  , merge
   , size
   , addresses
   , evolve
   , updateCells
   , cellAt
+  , safeCellAt
   , cells
   , neighboringAddresses
   , fate
@@ -18,7 +20,6 @@ module Life
 
 import Data.Array.IArray
 import Data.Array.Unboxed
-import Data.Word
 
 data Cell = Alive | Dead deriving (Show, Eq)
 type Dimension = Int
@@ -32,6 +33,17 @@ instance Show World where
 newWorld :: Address -> World
 newWorld worldSize = newWorldWithCells worldSize (cycle [Dead])
 
+merge :: World -> World -> World
+merge w1@(World ary1) w2@(World ary2) = World $ array
+                                                ((0,0), (maxX, maxY))
+                                                [ ((x,y), boolAt (x,y) ary1 || boolAt (x,y) ary2) | x <- [0..maxX], y <- [0..maxY] ]
+
+  where (width1, height1) = size w1
+        (width2, height2) = size w2
+        boolAt ix ary | inRange (bounds ary) ix = ary ! ix
+                      | otherwise = False
+        (maxX, maxY) = (max width1 width2 - 1, max height1 height2 - 1)
+
 toCell :: Bool -> Cell
 toCell True = Alive
 toCell False = Dead
@@ -47,7 +59,6 @@ size :: World -> Address
 size (World ary) = (maxX + 1, maxY + 1)
   where (maxX, maxY) = snd $ bounds ary
 
-
 addresses :: World -> [Address]
 addresses (World ary) = indices ary
 
@@ -62,6 +73,10 @@ updateCells updates (World ary) = World $ (ary // boolUpdates) where
 cellAt :: World -> Address -> Cell
 cellAt (World ary) ix = toCell (ary ! ix)
 
+safeCellAt :: World -> Address -> Cell
+safeCellAt w@(World ary) ix | inRange (bounds ary) ix = cellAt w ix
+                            | otherwise = Dead
+
 cells :: World -> [Cell]
 cells (World ary) = map toCell (elems ary)
 

src/Pattern.hs

@@ -8,7 +8,7 @@ module Pattern
 import Data.List
 import Life
 
-data Pattern = Pattern ![(Address, Cell)] deriving (Show)
+data Pattern = Pattern { patternCells :: [(Address, Cell)] } deriving (Show)
 
 loadPattern :: FilePath -> IO Pattern
 loadPattern filePath = do
@@ -17,7 +17,7 @@ loadPattern filePath = do
       parseChar ' ' = Alive
       mapCell y x cell = (x+1, ((x,y), parseChar cell))
       mapRow y row = (y+1, snd $ mapAccumL (mapCell y) 0 row)
-      patternCells = snd $ mapAccumL mapRow 0 (lines fileContents)
+      !patternCells = snd $ mapAccumL mapRow 0 (lines fileContents)
   return $ Pattern (concat patternCells)
 
 drawPatternAt :: Address -> Pattern -> World -> World

src/Timeline/Slice.hs

@@ -37,7 +37,8 @@ newSlice f w t = Slice { world = w, tick = t, projection = f w t, slHistory = [(
 
 nextSlice :: Projector b -> Slice a -> Slice b
 nextSlice f s = let tick' = (tick s) + 1
-                    world' = evolve (head $ slUserWorlds s ++ [world s])
+                    world' | (not . null) (slUserWorlds s) = evolve (foldl1' merge $ slUserWorlds s)
+                           | otherwise = evolve (world s)
                 in Slice { tick = tick'
                          , projection = f world' tick'
                          , world = world'
@@ -52,7 +53,7 @@ addUserInput :: Tick -> (World -> World) -> Slice a -> Maybe (Slice a)
 addUserInput inputTick f s = do worldAtTimeOfInput <- lookup inputTick (slHistory s)
                                 -- evaluating strictly so any exceptions will be raised while request is still being handled
                                 let !userWorld = evolveUpTo (f worldAtTimeOfInput) inputTick (tick s)
-                                return $ s { slUserWorlds = [ userWorld ] }
+                                return $ s { slUserWorlds = userWorld : slUserWorlds s }
   where evolveUpTo w t t' | t == t' = w
                           | otherwise = evolveUpTo (evolve w) (t + 1) t'
 

test/ArbitraryInstances.hs

@@ -1,6 +1,8 @@
 module ArbitraryInstances where
 
 import Control.Monad
+import Data.Function
+import Data.List
 import Data.Word
 
 import Test.QuickCheck.Gen
@@ -51,4 +53,4 @@ instance Arbitrary a => Arbitrary (Slice a) where
   arbitrary = liftM3 newSlice arbitrary arbitrary arbitrary
 
 instance Arbitrary Pattern where
-  arbitrary = liftM Pattern arbitrary
+  arbitrary = liftM Pattern (liftM (nubBy ((==) `on` fst)) arbitrary)

test/LifeTests.hs

@@ -35,4 +35,14 @@ tests = testGroup "Life"
       (fate Dead neighbors == Alive) == (length (filter (==Alive) neighbors) == 3)
   , "an Alive cell with 2 or 3 live neighbors lives" `testProperty` \(NeighborList neighbors) ->
       (fate Alive neighbors == Alive) == (length (filter (==Alive) neighbors) `elem` [2,3])
+
+  , "merge produces world big enough for both worlds" `testProperty` \world1 world2 ->
+      let (width1, height1) = size world1
+          (width2, height2) = size world2
+      in size (merge world1 world2) == (max width1 width2, max height1 height2)
+
+  , "merge favors life over death" `testProperty` \world1 world2 ->
+      let mergedWorld = merge world1 world2
+          mergedOk ix = (cellAt mergedWorld ix == Alive) == (safeCellAt world1 ix == Alive || safeCellAt world2 ix == Alive)
+      in all mergedOk (addresses mergedWorld)
   ]

test/Timeline/SliceTests.hs

@@ -35,17 +35,29 @@ tests = testGroup "Timeline.Slice" [
 
  ,"nextSlice evolves new world from current one" `testProperty` \slice (Blind projector) ->
       let _ = (slice, projector) :: (Slice (), Projector ())
-          slice' = nextSlice projector slice
-      in world slice' == evolve (world slice)
+      in world (nextSlice projector slice) == evolve (world slice)
 
  ,"nextSlice evolves from userInput if present" `testProperty` \slice (Blind projector) input ->
       let _ = (slice, projector) :: (Slice (), Projector ())
+
           Just sliceWithInput = addUserInput (tick slice) (drawPatternAt (0,0) input) slice
           slice' = nextSlice projector sliceWithInput
-          worldWithInput = (drawPatternAt (0,0) input $ world slice)
+          worldWithInput = drawPatternAt (0,0) input $ world slice
+
       in world slice' == evolve worldWithInput &&
          world (nextSlice projector slice') == (evolve . evolve) worldWithInput
 
+ ,"nextSlice unions multiple user inputs" `testProperty` \slice (Blind projector) input1 input2 ->
+      let _ = (slice, projector) :: (Slice (), Projector ())
+
+          Just sliceWithInput1 = addUserInput (tick slice) (drawPatternAt (0,0) input1) slice
+          Just sliceWithInput2 = addUserInput (tick slice) (drawPatternAt (0,0) input2) sliceWithInput1
+
+          worldWithInput1 = drawPatternAt (0,0) input1 (world slice)
+          worldWithInput2 = drawPatternAt (0,0) input2 (world slice)
+
+      in world (nextSlice projector sliceWithInput2) == evolve (merge worldWithInput1 worldWithInput2)
+
  ,"nextSlice evolves world from user historical input" `testProperty` \slice (Blind projector) input ->
       let _ = (slice, projector) :: (Slice (), Projector ())
           futureSlice = foldl (.) id (replicate 3 $ nextSlice projector) slice