Nice tank-border collision detection

src/Collision.hs

@@ -0,0 +1,41 @@
+module Collision ( collisionTankBorder
+                 ) where
+
+import Game
+
+import Data.Fixed
+import Data.Ratio
+
+tankWidth :: Micro
+tankWidth = 0.95
+
+tankLength :: Micro
+tankLength = 0.95
+
+collisionTankBorder :: Micro -> Micro -> Tank -> Tank
+collisionTankBorder lw lh tank = tank {tankX = newx, tankY = newy}
+    where
+      dir = (fromRational . toRational . tankDir $ tank)*pi/180
+      cosd = fromRational (round ((cos dir)*1000000)%1000000)
+      sind = fromRational (round ((sin dir)*1000000)%1000000)
+      
+      points = [ (tankLength/2, tankWidth/2)
+               , (-tankLength/2, tankWidth/2)
+               , (-tankLength/2, -tankWidth/2)
+               , (tankLength/2, -tankWidth/2)
+               ]
+      
+      rotp (x, y) = (cosd*x - sind*y, sind*x + cosd*y)
+      transp (x, y) = (x + tankX tank, y + tankY tank)
+      
+      pointst = map (transp . rotp) points
+      minx = minimum $ map fst pointst
+      maxx = maximum $ map fst pointst
+      miny = minimum $ map snd pointst
+      maxy = maximum $ map snd pointst
+      
+      dx = if minx < 0 then (-minx) else if maxx > lw then (-maxx+lw) else 0
+      dy = if miny < 0 then (-miny) else if maxy > lh then (-maxy+lh) else 0
+      
+      newx = (tankX tank) + dx
+      newy = (tankY tank) + dy