Take ore_rarity global accessable trough gravelsieve.ore_rarity

Unify check for optional maybe not existing ores
Removed not needed check against probability ~= nil (nil means does not exists, so "pairs" does not return them)

init.lua

@@ -38,23 +38,22 @@ gravelsieve.ore_rarity = tonumber(minetest.setting_get("gravelsieve_ore_rarity")
 
 
 -- Ore probability table  (1/n)
-local ore_probability = {
+gravelsieve.ore_probability = {
 	["default:iron_lump"] = 35,
 	["default:copper_lump"] = 60,
 	["default:tin_lump"] = 80,
 	["default:gold_lump"] = 175,
 	["default:mese_crystal"] = 275,
 	["default:diamond"] = 340,
+	["moreores:silver_lump"] = 100,
+	["moreores:mithril_lump"] = 250,
 }
 
-if minetest.get_modpath("moreores") then
+-- remove not registered ores from list
-	ore_probability["moreores:silver_lump"] = 100
+for ore, probability in pairs(gravelsieve.ore_probability) do
-	ore_probability["moreores:mithril_lump"] = 250
+	if not minetest.registered_items[ore] then
+		gravelsieve.ore_probability[ore] = nil
 	end
-
--- check if tin is available
-if ItemStack("default:tin_lump") == nil then
-	ore_probability["tin_lump"] = nil     -- not available
 end
 
 local sieve_formspec =
@@ -112,10 +111,9 @@ end
 -- place ores to dst according to the calculated probability
 local function random_ore(inv, src)
 	local num
-	for ore, probability in pairs(ore_probability) do
+	for ore, probability in pairs(gravelsieve.ore_probability) do
 		-- calculate the probability based on user configuration
 		probability = probability * gravelsieve.ore_rarity
-		if probability ~= nil then
 		if math.random(probability) == 1 then
 			local item = ItemStack(ore)
 			if inv:room_for_item("dst", item) then
@@ -124,7 +122,6 @@ local function random_ore(inv, src)
 			end
 		end
 	end
-	end
 	return false    -- gravel has to be moved
 end