[added] set module with full (-ish?) suite of set operations and efficient (non-linear) membership testing

closes #4

init.lua

@@ -1,22 +1,7 @@
 --[[
 	batteries for lua
 
-	if required as the "entire library" (ie by this file), puts everything into
-	global namespace by default as it'll presumably be commonly used
-
-	if not, several of the modules work as normal lua modules and return a table
-	for local-friendly use
-
-	the others that modify some global table can be talked into behaving as normal
-	lua modules as well by setting appropriate globals prior to inclusion
-
-	you can avoid modifying any global namespace by setting
-
-		BATTERIES_NO_GLOBALS = true
-
-	before requiring, then everything can be accessed as eg
-
-		batteries.table.stable_sort
+	a collection of helpful code to get your project off the ground faster
 ]]
 
 local path = ...
@@ -32,7 +17,9 @@ local _tablex = require_relative("tablex")
 local _stable_sort = require_relative("stable_sort")
 
 local _functional = require_relative("functional")
+
 local _sequence = require_relative("sequence")
+local _set = require_relative("set")
 
 local _stringx = require_relative("stringx")
 
@@ -69,8 +56,9 @@ local _batteries = {
 	sort = _stable_sort,
 	--
 	functional = _functional,
-	--
+	--collections
 	sequence = _sequence,
+	set = _set,
 	--geom
 	vec2 = _vec2,
 	vec3 = _vec3,
@@ -97,8 +85,9 @@ function _batteries:export(self)
 	--functional module also available separate from table
 	functional = _functional
 
-	--export sequence
+	--export collections
 	sequence = _sequence
+	set = _set
 
 	--overlay onto math
 	_tablex.overlay(math, _mathx)
@@ -111,7 +100,7 @@ function _batteries:export(self)
 	vec3 = _vec3
 	intersect = _intersect
 
-	--misc :)
+	--"misc" :)
 	unique_mapping = _unique_mapping
 	state_machine = _state_machine
 	async = _async

set.lua

@@ -0,0 +1,138 @@
+--[[
+	set type with appropriate operations
+]]
+
+local path = (...):gsub("set", "")
+local class = require(path .. "class")
+local table = require(path .. "tablex") --shadow global table module
+
+local set = class()
+
+--construct a new set
+--elements is an optional ordered table of elements to be added to the set
+function set:new(elements)
+	self = self:init({
+		_keyed = {},
+		_ordered = {},
+	})
+	if elements then
+		for _, v in ipairs(elements) do
+			self:add(v)
+		end
+	end
+	return self
+end
+
+--check if an element is present in the set
+function set:has(v)
+	return self._keyed[v] or false
+end
+
+--add a value to the set, if it's not already present
+function set:add(v)
+	if not self:has(v) then
+		self._keyed[v] = true
+		table.insert(self._ordered, v)
+	end
+	return self
+end
+
+--remove a value from the set, if it's present
+function set:remove(v)
+	if self:has(v) then
+		self._keyed[v] = nil
+		table.remove_value(self._ordered, v)
+	end
+	return self
+end
+
+--iterate the values in the set, along with their index
+--the index is useless but harmless, and adding a custom iterator seems
+--like a really easy way to encourage people to use slower-than-optimal code
+function set:ipairs()
+	return ipairs(self._ordered)
+end
+
+--get a copy of the values in the set, as a simple table
+function set:values()
+	return table.copy(self._ordered)
+end
+
+--modifying operations
+
+--add all the elements present in the other set
+function set:add_set(other)
+	for i, v in other:ipairs() do
+		self:add(v)
+	end
+	return self
+end
+
+--remove all the elements present in the other set
+function set:subtract_set(other)
+	for i, v in other:ipairs() do
+		self:remove(v)
+	end
+	return self
+end
+
+--new collection operations
+
+--copy a set
+function set:copy()
+	return set:new():add_set(self)
+end
+
+--create a new set containing the complement of the other set contained in this one
+--the elements present in this set but not present in the other set will remain in the result
+function set:complement(other)
+	return self:copy():subtract_set(other)
+end
+
+--alias
+set.difference = set.complement
+
+--create a new set containing the union of this set with another
+--an element present in either set will be present in the result
+function set:union(other)
+	return self:copy():add_set(other)
+end
+
+--create a new set containing the intersection of this set with another
+--only the elements present in both sets will remain in the result
+function set:intersection(other)
+	local r = set:new()
+	for i, v in self:ipairs() do
+		if other:has(v) then
+			r:add(v)
+		end
+	end
+	return r
+end
+
+--create a new set containing the symmetric difference of this set with another
+--only the elements not present in both sets will remain in the result
+--similiar to a logical XOR operation
+--
+--equal to self:union(other):subtract_set(self:intersection(other))
+--	but with much less wasted effort
+function set:symmetric_difference(other)
+	local r = set:new()
+	for i, v in self:ipairs() do
+		if not other:has(v) then
+			r:add(v)
+		end
+	end
+	for i, v in other:ipairs() do
+		if not self:has(v) then
+			r:add(v)
+		end
+	end
+	return r
+end
+
+--alias
+set.xor = set.symmetric_difference
+
+--
+return set