remove type from cell class

AliveCell.lua

@@ -3,7 +3,6 @@ AliveCell.__index = AliveCell
 
 function AliveCell.new(n)
 	local self = setmetatable({}, AliveCell)
-	self.type = "AliveCell"
 	return self
 end
 

Cell.lua

@@ -3,7 +3,6 @@ Cell.__index = Cell
 
 function Cell.new(n)
 	local self = setmetatable({}, Cell)
-	self.type = "Cell"
 	return self
 end
 

DeadCell.lua

@@ -3,7 +3,6 @@ DeadCell.__index = DeadCell
 
 function DeadCell.new(n)
 	local self = setmetatable({}, DeadCell)
-	self.type = "DeadCell"
 	return self
 end
 

World.lua

@@ -58,7 +58,7 @@ function World:neighbour(line, column)
 				and i<self.lines 
 				and j<self.columns
 			then
-				if self.grid[i][j].type == "AliveCell" then
+				if self.grid[i][j].__index == AliveCell then
 					neighbour=neighbour+1
 				end
 			end