From 8d294ca65fb68df542b7c04fe014d33b2aa556ea Mon Sep 17 00:00:00 2001
From: raymoo <uguu@installgentoo.com>
Date: Sun, 12 Jun 2016 22:15:08 -0700
Subject: [PATCH] standard monoids

---
 standard_monoids.lua | 180 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 180 insertions(+)
 create mode 100644 standard_monoids.lua

diff --git a/standard_monoids.lua b/standard_monoids.lua
new file mode 100644
index 0000000..34d7658
--- /dev/null
+++ b/standard_monoids.lua
@@ -0,0 +1,180 @@
+-- Standard effect monoids, to provide canonicity.
+
+local function mult(x, y) return x * y end
+
+local function mult_fold(elems)
+	local tot = 1
+
+	for k,v in pairs(elems) do
+		tot = tot * v
+	end
+
+	return tot
+end
+
+local function v_mult(v1, v2)
+	local res = {}
+
+	for k, v in pairs(v1) do
+		res[k] = v * v2[k]
+	end
+
+	return res
+end
+
+local function v_mult_fold(identity)
+	return function(elems)
+		local tot = identity
+
+		for k, v in pairs(elems) do
+			tot = v_mult(tot, v)
+		end
+
+		return tot
+	end
+end
+
+local monoid = player_monoids.monoid
+
+-- Speed monoid. Effect values are speed multipliers. Must be nonnegative
+-- numbers.
+player_monoids.speed = monoid({
+	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.
+player_monoids.jump = monoid({
+	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.
+player_monoids.gravity = monoid({
+	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,
+})
+
+
+-- Fly ability monoid. The values are booleans, which are combined by or. A true
+-- value indicates having the ability to fly.
+player_monoids.fly = monoid({
+	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.
+player_monoids.noclip = monoid({
+	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,
+})
+
+local def_col_scale = { x=0.3, y=1, z=0.3 }
+
+-- Collisionbox scaling factor. Values are a vector of x, y, z multipliers.
+player_monoids.collisionbox = monoid({
+	combine = v_mult,
+	fold = v_mult_fold({x=1, y=1, z=1}),
+	identity = {x=1, y=1, z=1},
+	apply = function(multiplier, player)
+		local v = vector.multiply(def_col_scale, multiplier)
+
+		player:set_properties({
+			collisionbox = { -v.x, -v.y, -v.z, v.z, v.y, v.z }
+		})
+	end,
+})
+
+player_monoids.visual_size = monoid({
+	combine = v_mult,
+	fold = v_mult_fold({x=1, y=1}),
+	identity = {x=1, y=1},
+	apply = function(multiplier, player)
+		player:set_properties({
+			visual_size = multiplier
+		})
+	end,
+})