Add .luacheckrc and fix warnings.

.luacheckrc

@@ -0,0 +1,9 @@
+
+read_globals = {
+	"minetest",
+	"vector",
+}
+
+globals = {
+	"player_monoids",
+}

standard_monoids.lua

@@ -1,17 +1,5 @@
 -- 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 = {}
 
@@ -26,7 +14,7 @@ local function v_mult_fold(identity)
 	return function(elems)
 		local tot = identity
 
-		for k, v in pairs(elems) do
+		for _, v in pairs(elems) do
 			tot = v_mult(tot, v)
 		end
 
@@ -42,7 +30,7 @@ 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
+		for _, v in pairs(elems) do
 			res = res * v
 		end
 
@@ -63,7 +51,7 @@ 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
+		for _, v in pairs(elems) do
 			res = res * v
 		end
 
@@ -83,7 +71,7 @@ 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
+		for _, v in pairs(elems) do
 			res = res * v
 		end
 
@@ -103,7 +91,7 @@ player_monoids.gravity = monoid({
 player_monoids.fly = monoid({
 	combine = function(p, q) return p or q end,
 	fold = function(elems)
-		for k, v in pairs(elems) do
+		for _, v in pairs(elems) do
 			if v then return true end
 		end
 
@@ -130,7 +118,7 @@ player_monoids.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
+		for _, v in pairs(elems) do
 			if v then return true end
 		end