diff --git a/init.lua b/init.lua
index 1e24c42..ed34bdf 100644
--- a/init.lua
+++ b/init.lua
@@ -4,7 +4,7 @@
 -- Any documentation here are internal details, please avoid using them in your
 -- mod.
 
-local modpath = minetest.get_modpath(minetest.get_current_modname())
+local modpath = minetest.get_modpath(minetest.get_current_modname()) .. "/"
 
 player_monoids = {}
 
@@ -12,6 +12,8 @@ local mon_meta = {}
 
 mon_meta.__index = mon_meta
 
+local nop = function() end
+
 -- A monoid object is a table with the following fields:
 --   def: The monoid definition
 --   player_map: A map from player names to their effect tables. Effect tables
@@ -22,6 +24,22 @@ mon_meta.__index = mon_meta
 local function monoid(def)
 	local mon = {}
 
+	local actual_def = {}
+
+	for k, v in pairs(def) do
+		actual_def[k] = v
+	end
+
+	if not actual_def.apply then
+		actual_def.apply = nop
+	end
+
+	if not actual_def.on_change then
+		actual_def.on_change = nop
+	end
+
+	mon.def = actual_def
+
 	local p_map = {}
         mon.player_map = p_map
 
@@ -30,7 +48,7 @@ local function monoid(def)
 	local v_cache = {}
 	mon.value_cache = v_cache
 
-	setmetatable(mon, mon_methods)
+	setmetatable(mon, mon_meta)
 
 	minetest.register_on_leaveplayer(function(player)
 		local p_name = player:get_player_name()
@@ -41,7 +59,7 @@ local function monoid(def)
 	return mon
 end
 
-player_monoids.make_monoid = monoid
+player_monoids.monoid = monoid
 
 function mon_meta:add_change(player, value)
 	local p_name = player:get_player_name()
@@ -67,14 +85,18 @@ function mon_meta:add_change(player, value)
 	p_effects[actual_id] = value
 	local new_total = def.fold(p_effects)
 	self.value_cache[p_name] = new_total
-        
+
 	def.apply(new_total, player)
 	def.on_change(old_total, new_total, player)
+
+	return actual_id
 end
 
 function mon_meta:del_change(player, id)
 	local p_name = player:get_player_name()
 
+	local def = self.def
+
 	local p_effects = self.player_map[p_name]
 	if p_effects == nil then return end
 
@@ -91,3 +113,6 @@ function mon_meta:value(player)
 	local p_name = player:get_player_name()
 	return self.value_cache[p_name] or self.def.identity
 end
+
+dofile(modpath .. "standard_monoids.lua")
+dofile(modpath .. "test.lua")