Standard monoids

standard_monoids.lua

@@ -0,0 +1,136 @@
+-- Standard effect monoids, to provide canonicity.
+
+-- Speed monoid. Effect values are speed multipliers. Must be nonnegative
+-- numbers.
+monoidal_effects.register_monoid("speed",
+				 { combine = function(x, y) return x * y end,
+				   fold = function(elems)
+					   local res = 1
+					   for k, v in pairs(elems) do
+						   res = res * v
+					   end
+
+					   return res
+				   end,
+				   identity = 1,
+				   apply = function(mult, player)
+					   local ov = player:get_physics_override()
+					   ov.speed = mult
+					   player:set_physics_override(ov)
+				   end,
+})
+
+
+-- Jump monoid. Effect values are jump multipliers. Must be nonnegative
+-- numbers.
+monoidal_effects.register_monoid("jump",
+				 { combine = function(x, y) return x * y end,
+				   fold = function(elems)
+					   local res = 1
+					   for k, v in pairs(elems) do
+						   res = res * v
+					   end
+
+					   return res
+				   end,
+				   identity = 1,
+				   apply = function(mult, player)
+					   local ov = player:get_physics_override()
+					   ov.jump = mult
+					   player:set_physics_override(ov)
+				   end,
+})
+
+
+-- Gravity monoid. Effect values are gravity multipliers.
+monoidal_effects.register_monoid("gravity",
+				 { combine = function(x, y) return x * y end,
+				   fold = function(elems)
+					   local res = 1
+					   for k, v in pairs(elems) do
+						   res = res * v
+					   end
+
+					   return res
+				   end,
+				   identity = 1,
+				   apply = function(mult, player)
+					   local ov = player:get_physics_override()
+					   ov.gravity = mult
+					   player:set_physics_override(ov)
+				   end,
+})
+
+
+-- Max HP modifier monoid. It combines by addition. Values should be nonnegative
+-- integers.
+monoidal_effects.register_monoid("hp_max",
+				 { combine = function(x, y) return x + y end,
+				   fold = function(elems)
+					   local res = 0
+					   for k, v in pairs(elems) do
+						   res = res + v
+					   end
+
+					   return res
+				   end,
+				   identity = 0,
+				   apply = function(offset, player)
+					   player:set_properties({ hp_max = offset + 20 })
+				   end,
+})
+
+
+-- Fly ability monoid. The values are booleans, which are combined by or. A true
+-- value indicates having the ability to fly.
+monoidal_effects.register_monoid("fly",
+				 { combine = function(p, q) return p or q end,
+				   fold = function(elems)
+					   for k, v in pairs(elems) do
+						   if v then return true end
+					   end
+
+					   return false
+				   end,
+				   identity = false,
+				   apply = function(can_fly, player)
+					   local p_name = player:get_player_name()
+					   local privs = minetest.get_player_privs(p_name)
+					   
+					   if can_fly then
+						   privs.fly = true
+					   else
+						   privs.fly = nil
+					   end
+
+					   minetest.set_player_privs(p_name, privs)
+
+				   end,
+})
+
+
+-- Noclip ability monoid. Works the same as fly monoid.
+monoidal_effects.register_monoid("noclip",
+				 { combine = function(p, q) return p or q end,
+				   fold = function(elems)
+					   for k, v in pairs(elems) do
+						   if v then return true end
+					   end
+
+					   return false
+				   end,
+				   identity = false,
+				   apply = function(can_noclip, player)
+					   local p_name = player:get_player_name()
+					   local privs = minetest.get_player_privs(p_name)
+					   
+					   if can_noclip then
+						   privs.noclip = true
+					   else
+						   privs.noclip = nil
+					   end
+
+					   minetest.set_player_privs(p_name, privs)
+
+				   end,
+})