add class() for easy definition of classes

code/class.lua

@@ -0,0 +1,7 @@
+function class(super, self)
+	assert(super == nil or super.__index == super)
+	self = self or {}
+	self.__index = self
+	setmetatable(self, super)
+	return self
+end

code/entities/decoration.lua

@@ -1,8 +1,8 @@
-Decoration = {}
-Decoration.type = "Decoration"
-Decoration.supertype = Entity.type
-Decoration.display = Animation:new(animation.particle.simple)
-setmetatable(Decoration, Entity)
+Decoration = class(Entity, {
+	type = "Decoration",
+	supertype = Entity.type,
+	display = Animation:new(animation.particle.simple),
+})
 
 function Decoration:new(x,y,animation,light_data)
 	local o = Entity:new(x,y)
@@ -22,7 +22,6 @@ function Decoration:new(x,y,animation,light_data)
 	o:id()
 
 	setmetatable(o, self)
-	self.__index = self
 	return o
 end
 

code/entity.lua

@@ -1,6 +1,5 @@
 LoadedObjects.Entities = {}
-Entity = {}
-Entity.type = "Entity"
+Entity = class(nil, {type = "Entity"})
 
 function Entity:new(x,y)
 	local o = {}
@@ -26,7 +25,6 @@ function Entity:new(x,y)
 	o.sprite_flip = { x = 1, y = 1}
 
 	setmetatable(o, self)
-	self.__index = self
 	return o
 end
 

code/require.lua

@@ -7,6 +7,7 @@ require "data/sfx"
 require "code/locale"
 
 -- support functions
+require "code/class"
 require "code/math"
 require "code/draw"
 require "code/hex"