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Difference between revisions of "Module:TableTools"

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--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--                               TableTools                                       --
+
--                                   TableTools                                   --
 
--                                                                                --
 
--                                                                                --
 
-- This module includes a number of functions for dealing with Lua tables.        --
 
-- This module includes a number of functions for dealing with Lua tables.        --
-- It is a meta-module, meant to be called from other Lua modules, and should     --
+
-- It is a meta-module, meant to be called from other Lua modules, and should not --
-- not be called directly from #invoke.                                           --
+
-- be called directly from #invoke.                                               --
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
  
 
local libraryUtil = require('libraryUtil')
 
local libraryUtil = require('libraryUtil')
Line 17: Line 15:
 
local infinity = math.huge
 
local infinity = math.huge
 
local checkType = libraryUtil.checkType
 
local checkType = libraryUtil.checkType
 +
local checkTypeMulti = libraryUtil.checkTypeMulti
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- isPositiveInteger
 
-- isPositiveInteger
Line 27: Line 25:
 
-- hash part of a table.
 
-- hash part of a table.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.isPositiveInteger(v)
 
function p.isPositiveInteger(v)
if type(v) == 'number' and v >= 1 and floor(v) == v and v < infinity then
+
return type(v) == 'number' and v >= 1 and floor(v) == v and v < infinity
return true
 
else
 
return false
 
end
 
 
end
 
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- isNan
 
-- isNan
 
--
 
--
-- This function returns true if the given number is a NaN value, and false
+
-- This function returns true if the given number is a NaN value, and false if
-- if not. Although it doesn't operate on tables, it is included here as it is
+
-- not. Although it doesn't operate on tables, it is included here as it is useful
-- useful for determining whether a value can be a valid table key. Lua will
+
-- for determining whether a value can be a valid table key. Lua will generate an
-- generate an error if a NaN is used as a table key.
+
-- error if a NaN is used as a table key.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.isNan(v)
 
function p.isNan(v)
if type(v) == 'number' and tostring(v) == '-nan' then
+
return type(v) == 'number' and v ~= v
return true
 
else
 
return false
 
end
 
 
end
 
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- shallowClone
 
-- shallowClone
Line 62: Line 48:
 
-- table will have no metatable of its own.
 
-- table will have no metatable of its own.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.shallowClone(t)
 
function p.shallowClone(t)
 +
checkType('shallowClone', 1, t, 'table')
 
local ret = {}
 
local ret = {}
 
for k, v in pairs(t) do
 
for k, v in pairs(t) do
Line 71: Line 57:
 
end
 
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- removeDuplicates
 
-- removeDuplicates
Line 79: Line 64:
 
-- removed, but otherwise the array order is unchanged.
 
-- removed, but otherwise the array order is unchanged.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
+
function p.removeDuplicates(arr)
function p.removeDuplicates(t)
+
checkType('removeDuplicates', 1, arr, 'table')
checkType('removeDuplicates', 1, t, 'table')
 
 
local isNan = p.isNan
 
local isNan = p.isNan
 
local ret, exists = {}, {}
 
local ret, exists = {}, {}
for i, v in ipairs(t) do
+
for _, v in ipairs(arr) do
 
if isNan(v) then
 
if isNan(v) then
 
-- NaNs can't be table keys, and they are also unique, so we don't need to check existence.
 
-- NaNs can't be table keys, and they are also unique, so we don't need to check existence.
Line 93: Line 77:
 
exists[v] = true
 
exists[v] = true
 
end
 
end
end
+
end
 
end
 
end
 
return ret
 
return ret
end
+
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- numKeys
 
-- numKeys
Line 105: Line 88:
 
-- keys that have non-nil values, sorted in numerical order.
 
-- keys that have non-nil values, sorted in numerical order.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.numKeys(t)
 
function p.numKeys(t)
 
checkType('numKeys', 1, t, 'table')
 
checkType('numKeys', 1, t, 'table')
 
local isPositiveInteger = p.isPositiveInteger
 
local isPositiveInteger = p.isPositiveInteger
 
local nums = {}
 
local nums = {}
for k, v in pairs(t) do
+
for k in pairs(t) do
 
if isPositiveInteger(k) then
 
if isPositiveInteger(k) then
 
nums[#nums + 1] = k
 
nums[#nums + 1] = k
Line 119: Line 101:
 
end
 
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- affixNums
 
-- affixNums
Line 125: Line 106:
 
-- This takes a table and returns an array containing the numbers of keys with the
 
-- This takes a table and returns an array containing the numbers of keys with the
 
-- specified prefix and suffix. For example, for the table
 
-- specified prefix and suffix. For example, for the table
-- {a1 = 'foo', a3 = 'bar', a6 = 'baz'} and the prefix "a", affixNums will
+
-- {a1 = 'foo', a3 = 'bar', a6 = 'baz'} and the prefix "a", affixNums will return
-- return {1, 3, 6}.
+
-- {1, 3, 6}.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.affixNums(t, prefix, suffix)
 
function p.affixNums(t, prefix, suffix)
 
checkType('affixNums', 1, t, 'table')
 
checkType('affixNums', 1, t, 'table')
Line 136: Line 116:
 
local function cleanPattern(s)
 
local function cleanPattern(s)
 
-- Cleans a pattern so that the magic characters ()%.[]*+-?^$ are interpreted literally.
 
-- Cleans a pattern so that the magic characters ()%.[]*+-?^$ are interpreted literally.
s = s:gsub('([%(%)%%%.%[%]%*%+%-%?%^%$])', '%%%1')
+
return s:gsub('([%(%)%%%.%[%]%*%+%-%?%^%$])', '%%%1')
return s
 
 
end
 
end
  
Line 147: Line 126:
  
 
local nums = {}
 
local nums = {}
for k, v in pairs(t) do
+
for k in pairs(t) do
if type(k) == 'string' then
+
if type(k) == 'string' then
 
local num = mw.ustring.match(k, pattern)
 
local num = mw.ustring.match(k, pattern)
 
if num then
 
if num then
Line 159: Line 138:
 
end
 
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- numData
 
-- numData
 
--
 
--
-- Given a table with keys like ("foo1", "bar1", "foo2", "baz2"), returns a table
+
-- Given a table with keys like {"foo1", "bar1", "foo2", "baz2"}, returns a table
-- of subtables in the format  
+
-- of subtables in the format
-- { [1] = {foo = 'text', bar = 'text'}, [2] = {foo = 'text', baz = 'text'} }
+
-- {[1] = {foo = 'text', bar = 'text'}, [2] = {foo = 'text', baz = 'text'}}.
-- Keys that don't end with an integer are stored in a subtable named "other".
+
-- Keys that don't end with an integer are stored in a subtable named "other". The
-- The compress option compresses the table so that it can be iterated over with
+
-- compress option compresses the table so that it can be iterated over with
 
-- ipairs.
 
-- ipairs.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.numData(t, compress)
 
function p.numData(t, compress)
 
checkType('numData', 1, t, 'table')
 
checkType('numData', 1, t, 'table')
Line 200: Line 177:
 
end
 
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- compressSparseArray
 
-- compressSparseArray
Line 208: Line 184:
 
-- ipairs.
 
-- ipairs.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.compressSparseArray(t)
 
function p.compressSparseArray(t)
 
checkType('compressSparseArray', 1, t, 'table')
 
checkType('compressSparseArray', 1, t, 'table')
Line 219: Line 194:
 
end
 
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- sparseIpairs
 
-- sparseIpairs
Line 226: Line 200:
 
-- handle nil values.
 
-- handle nil values.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.sparseIpairs(t)
 
function p.sparseIpairs(t)
 
checkType('sparseIpairs', 1, t, 'table')
 
checkType('sparseIpairs', 1, t, 'table')
Line 243: Line 216:
 
end
 
end
  
--[[
 
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
 
-- size
 
-- size
Line 250: Line 222:
 
-- but for arrays it is more efficient to use the # operator.
 
-- but for arrays it is more efficient to use the # operator.
 
------------------------------------------------------------------------------------
 
------------------------------------------------------------------------------------
--]]
 
 
function p.size(t)
 
function p.size(t)
 
checkType('size', 1, t, 'table')
 
checkType('size', 1, t, 'table')
 
local i = 0
 
local i = 0
 +
for _ in pairs(t) do
 +
i = i + 1
 +
end
 +
return i
 +
end
 +
 +
local function defaultKeySort(item1, item2)
 +
-- "number" < "string", so numbers will be sorted before strings.
 +
local type1, type2 = type(item1), type(item2)
 +
if type1 ~= type2 then
 +
return type1 < type2
 +
elseif type1 == 'table' or type1 == 'boolean' or type1 == 'function' then
 +
return tostring(item1) < tostring(item2)
 +
else
 +
return item1 < item2
 +
end
 +
end
 +
------------------------------------------------------------------------------------
 +
-- keysToList
 +
--
 +
-- Returns an array of the keys in a table, sorted using either a default
 +
-- comparison function or a custom keySort function.
 +
------------------------------------------------------------------------------------
 +
function p.keysToList(t, keySort, checked)
 +
if not checked then
 +
checkType('keysToList', 1, t, 'table')
 +
checkTypeMulti('keysToList', 2, keySort, {'function', 'boolean', 'nil'})
 +
end
 +
 +
local arr = {}
 +
local index = 1
 
for k in pairs(t) do
 
for k in pairs(t) do
 +
arr[index] = k
 +
index = index + 1
 +
end
 +
 +
if keySort ~= false then
 +
keySort = type(keySort) == 'function' and keySort or defaultKeySort
 +
table.sort(arr, keySort)
 +
end
 +
 +
return arr
 +
end
 +
 +
------------------------------------------------------------------------------------
 +
-- sortedPairs
 +
--
 +
-- Iterates through a table, with the keys sorted using the keysToList function.
 +
-- If there are only numerical keys, sparseIpairs is probably more efficient.
 +
------------------------------------------------------------------------------------
 +
function p.sortedPairs(t, keySort)
 +
checkType('sortedPairs', 1, t, 'table')
 +
checkType('sortedPairs', 2, keySort, 'function', true)
 +
 +
local arr = p.keysToList(t, keySort, true)
 +
 +
local i = 0
 +
return function ()
 +
i = i + 1
 +
local key = arr[i]
 +
if key ~= nil then
 +
return key, t[key]
 +
else
 +
return nil, nil
 +
end
 +
end
 +
end
 +
 +
------------------------------------------------------------------------------------
 +
-- isArray
 +
--
 +
-- Returns true if the given value is a table and all keys are consecutive
 +
-- integers starting at 1.
 +
------------------------------------------------------------------------------------
 +
function p.isArray(v)
 +
if type(v) ~= 'table' then
 +
return false
 +
end
 +
local i = 0
 +
for _ in pairs(v) do
 +
i = i + 1
 +
if v[i] == nil then
 +
return false
 +
end
 +
end
 +
return true
 +
end
 +
 +
------------------------------------------------------------------------------------
 +
-- isArrayLike
 +
--
 +
-- Returns true if the given value is iterable and all keys are consecutive
 +
-- integers starting at 1.
 +
------------------------------------------------------------------------------------
 +
function p.isArrayLike(v)
 +
if not pcall(pairs, v) then
 +
return false
 +
end
 +
local i = 0
 +
for _ in pairs(v) do
 
i = i + 1
 
i = i + 1
 +
if v[i] == nil then
 +
return false
 +
end
 +
end
 +
return true
 +
end
 +
 +
------------------------------------------------------------------------------------
 +
-- invert
 +
--
 +
-- Transposes the keys and values in an array. For example, {"a", "b", "c"} ->
 +
-- {a = 1, b = 2, c = 3}. Duplicates are not supported (result values refer to
 +
-- the index of the last duplicate) and NaN values are ignored.
 +
------------------------------------------------------------------------------------
 +
function p.invert(arr)
 +
checkType("invert", 1, arr, "table")
 +
local isNan = p.isNan
 +
local map = {}
 +
for i, v in ipairs(arr) do
 +
if not isNan(v) then
 +
map[v] = i
 +
end
 
end
 
end
return i
+
 
 +
return map
 +
end
 +
 
 +
------------------------------------------------------------------------------------
 +
-- listToSet
 +
--
 +
-- Creates a set from the array part of the table. Indexing the set by any of the
 +
-- values of the array returns true. For example, {"a", "b", "c"} ->
 +
-- {a = true, b = true, c = true}. NaN values are ignored as Lua considers them
 +
-- never equal to any value (including other NaNs or even themselves).
 +
------------------------------------------------------------------------------------
 +
function p.listToSet(arr)
 +
checkType("listToSet", 1, arr, "table")
 +
local isNan = p.isNan
 +
local set = {}
 +
for _, v in ipairs(arr) do
 +
if not isNan(v) then
 +
set[v] = true
 +
end
 +
end
 +
 
 +
return set
 +
end
 +
 
 +
------------------------------------------------------------------------------------
 +
-- deepCopy
 +
--
 +
-- Recursive deep copy function. Preserves identities of subtables.
 +
------------------------------------------------------------------------------------
 +
local function _deepCopy(orig, includeMetatable, already_seen)
 +
-- Stores copies of tables indexed by the original table.
 +
already_seen = already_seen or {}
 +
 
 +
local copy = already_seen[orig]
 +
if copy ~= nil then
 +
return copy
 +
end
 +
 
 +
if type(orig) == 'table' then
 +
copy = {}
 +
for orig_key, orig_value in pairs(orig) do
 +
copy[_deepCopy(orig_key, includeMetatable, already_seen)] = _deepCopy(orig_value, includeMetatable, already_seen)
 +
end
 +
already_seen[orig] = copy
 +
 
 +
if includeMetatable then
 +
local mt = getmetatable(orig)
 +
if mt ~= nil then
 +
local mt_copy = _deepCopy(mt, includeMetatable, already_seen)
 +
setmetatable(copy, mt_copy)
 +
already_seen[mt] = mt_copy
 +
end
 +
end
 +
else -- number, string, boolean, etc
 +
copy = orig
 +
end
 +
return copy
 +
end
 +
 
 +
function p.deepCopy(orig, noMetatable, already_seen)
 +
checkType("deepCopy", 3, already_seen, "table", true)
 +
return _deepCopy(orig, not noMetatable, already_seen)
 +
end
 +
 
 +
------------------------------------------------------------------------------------
 +
-- sparseConcat
 +
--
 +
-- Concatenates all values in the table that are indexed by a number, in order.
 +
-- sparseConcat{a, nil, c, d}  =>  "acd"
 +
-- sparseConcat{nil, b, c, d}  =>  "bcd"
 +
------------------------------------------------------------------------------------
 +
function p.sparseConcat(t, sep, i, j)
 +
local arr = {}
 +
 
 +
local arr_i = 0
 +
for _, v in p.sparseIpairs(t) do
 +
arr_i = arr_i + 1
 +
arr[arr_i] = v
 +
end
 +
 
 +
return table.concat(arr, sep, i, j)
 +
end
 +
 
 +
------------------------------------------------------------------------------------
 +
-- length
 +
--
 +
-- Finds the length of an array, or of a quasi-array with keys such as "data1",
 +
-- "data2", etc., using an exponential search algorithm. It is similar to the
 +
-- operator #, but may return a different value when there are gaps in the array
 +
-- portion of the table. Intended to be used on data loaded with mw.loadData. For
 +
-- other tables, use #.
 +
-- Note: #frame.args in frame object always be set to 0, regardless of  the number
 +
-- of unnamed template parameters, so use this function for frame.args.
 +
------------------------------------------------------------------------------------
 +
function p.length(t, prefix)
 +
-- requiring module inline so that [[Module:Exponential search]] which is
 +
-- only needed by this one function doesn't get millions of transclusions
 +
local expSearch = require("Module:Exponential search")
 +
checkType('length', 1, t, 'table')
 +
checkType('length', 2, prefix, 'string', true)
 +
return expSearch(function (i)
 +
local key
 +
if prefix then
 +
key = prefix .. tostring(i)
 +
else
 +
key = i
 +
end
 +
return t[key] ~= nil
 +
end) or 0
 +
end
 +
 
 +
------------------------------------------------------------------------------------
 +
-- inArray
 +
--
 +
-- Returns true if valueToFind is a member of the array, and false otherwise.
 +
------------------------------------------------------------------------------------
 +
function p.inArray(arr, valueToFind)
 +
checkType("inArray", 1, arr, "table")
 +
-- if valueToFind is nil, error?
 +
 
 +
for _, v in ipairs(arr) do
 +
if v == valueToFind then
 +
return true
 +
end
 +
end
 +
return false
 
end
 
end
  
 
return p
 
return p

Latest revision as of 00:36, 19 January 2024

Documentation for this module may be created at Module:TableTools/doc

------------------------------------------------------------------------------------
--                                   TableTools                                   --
--                                                                                --
-- This module includes a number of functions for dealing with Lua tables.        --
-- It is a meta-module, meant to be called from other Lua modules, and should not --
-- be called directly from #invoke.                                               --
------------------------------------------------------------------------------------

local libraryUtil = require('libraryUtil')

local p = {}

-- Define often-used variables and functions.
local floor = math.floor
local infinity = math.huge
local checkType = libraryUtil.checkType
local checkTypeMulti = libraryUtil.checkTypeMulti

------------------------------------------------------------------------------------
-- isPositiveInteger
--
-- This function returns true if the given value is a positive integer, and false
-- if not. Although it doesn't operate on tables, it is included here as it is
-- useful for determining whether a given table key is in the array part or the
-- hash part of a table.
------------------------------------------------------------------------------------
function p.isPositiveInteger(v)
	return type(v) == 'number' and v >= 1 and floor(v) == v and v < infinity
end

------------------------------------------------------------------------------------
-- isNan
--
-- This function returns true if the given number is a NaN value, and false if
-- not. Although it doesn't operate on tables, it is included here as it is useful
-- for determining whether a value can be a valid table key. Lua will generate an
-- error if a NaN is used as a table key.
------------------------------------------------------------------------------------
function p.isNan(v)
	return type(v) == 'number' and v ~= v
end

------------------------------------------------------------------------------------
-- shallowClone
--
-- This returns a clone of a table. The value returned is a new table, but all
-- subtables and functions are shared. Metamethods are respected, but the returned
-- table will have no metatable of its own.
------------------------------------------------------------------------------------
function p.shallowClone(t)
	checkType('shallowClone', 1, t, 'table')
	local ret = {}
	for k, v in pairs(t) do
		ret[k] = v
	end
	return ret
end

------------------------------------------------------------------------------------
-- removeDuplicates
--
-- This removes duplicate values from an array. Non-positive-integer keys are
-- ignored. The earliest value is kept, and all subsequent duplicate values are
-- removed, but otherwise the array order is unchanged.
------------------------------------------------------------------------------------
function p.removeDuplicates(arr)
	checkType('removeDuplicates', 1, arr, 'table')
	local isNan = p.isNan
	local ret, exists = {}, {}
	for _, v in ipairs(arr) do
		if isNan(v) then
			-- NaNs can't be table keys, and they are also unique, so we don't need to check existence.
			ret[#ret + 1] = v
		else
			if not exists[v] then
				ret[#ret + 1] = v
				exists[v] = true
			end
		end
	end
	return ret
end

------------------------------------------------------------------------------------
-- numKeys
--
-- This takes a table and returns an array containing the numbers of any numerical
-- keys that have non-nil values, sorted in numerical order.
------------------------------------------------------------------------------------
function p.numKeys(t)
	checkType('numKeys', 1, t, 'table')
	local isPositiveInteger = p.isPositiveInteger
	local nums = {}
	for k in pairs(t) do
		if isPositiveInteger(k) then
			nums[#nums + 1] = k
		end
	end
	table.sort(nums)
	return nums
end

------------------------------------------------------------------------------------
-- affixNums
--
-- This takes a table and returns an array containing the numbers of keys with the
-- specified prefix and suffix. For example, for the table
-- {a1 = 'foo', a3 = 'bar', a6 = 'baz'} and the prefix "a", affixNums will return
-- {1, 3, 6}.
------------------------------------------------------------------------------------
function p.affixNums(t, prefix, suffix)
	checkType('affixNums', 1, t, 'table')
	checkType('affixNums', 2, prefix, 'string', true)
	checkType('affixNums', 3, suffix, 'string', true)

	local function cleanPattern(s)
		-- Cleans a pattern so that the magic characters ()%.[]*+-?^$ are interpreted literally.
		return s:gsub('([%(%)%%%.%[%]%*%+%-%?%^%$])', '%%%1')
	end

	prefix = prefix or ''
	suffix = suffix or ''
	prefix = cleanPattern(prefix)
	suffix = cleanPattern(suffix)
	local pattern = '^' .. prefix .. '([1-9]%d*)' .. suffix .. '$'

	local nums = {}
	for k in pairs(t) do
		if type(k) == 'string' then
			local num = mw.ustring.match(k, pattern)
			if num then
				nums[#nums + 1] = tonumber(num)
			end
		end
	end
	table.sort(nums)
	return nums
end

------------------------------------------------------------------------------------
-- numData
--
-- Given a table with keys like {"foo1", "bar1", "foo2", "baz2"}, returns a table
-- of subtables in the format
-- {[1] = {foo = 'text', bar = 'text'}, [2] = {foo = 'text', baz = 'text'}}.
-- Keys that don't end with an integer are stored in a subtable named "other". The
-- compress option compresses the table so that it can be iterated over with
-- ipairs.
------------------------------------------------------------------------------------
function p.numData(t, compress)
	checkType('numData', 1, t, 'table')
	checkType('numData', 2, compress, 'boolean', true)
	local ret = {}
	for k, v in pairs(t) do
		local prefix, num = mw.ustring.match(tostring(k), '^([^0-9]*)([1-9][0-9]*)$')
		if num then
			num = tonumber(num)
			local subtable = ret[num] or {}
			if prefix == '' then
				-- Positional parameters match the blank string; put them at the start of the subtable instead.
				prefix = 1
			end
			subtable[prefix] = v
			ret[num] = subtable
		else
			local subtable = ret.other or {}
			subtable[k] = v
			ret.other = subtable
		end
	end
	if compress then
		local other = ret.other
		ret = p.compressSparseArray(ret)
		ret.other = other
	end
	return ret
end

------------------------------------------------------------------------------------
-- compressSparseArray
--
-- This takes an array with one or more nil values, and removes the nil values
-- while preserving the order, so that the array can be safely traversed with
-- ipairs.
------------------------------------------------------------------------------------
function p.compressSparseArray(t)
	checkType('compressSparseArray', 1, t, 'table')
	local ret = {}
	local nums = p.numKeys(t)
	for _, num in ipairs(nums) do
		ret[#ret + 1] = t[num]
	end
	return ret
end

------------------------------------------------------------------------------------
-- sparseIpairs
--
-- This is an iterator for sparse arrays. It can be used like ipairs, but can
-- handle nil values.
------------------------------------------------------------------------------------
function p.sparseIpairs(t)
	checkType('sparseIpairs', 1, t, 'table')
	local nums = p.numKeys(t)
	local i = 0
	local lim = #nums
	return function ()
		i = i + 1
		if i <= lim then
			local key = nums[i]
			return key, t[key]
		else
			return nil, nil
		end
	end
end

------------------------------------------------------------------------------------
-- size
--
-- This returns the size of a key/value pair table. It will also work on arrays,
-- but for arrays it is more efficient to use the # operator.
------------------------------------------------------------------------------------
function p.size(t)
	checkType('size', 1, t, 'table')
	local i = 0
	for _ in pairs(t) do
		i = i + 1
	end
	return i
end

local function defaultKeySort(item1, item2)
	-- "number" < "string", so numbers will be sorted before strings.
	local type1, type2 = type(item1), type(item2)
	if type1 ~= type2 then
		return type1 < type2
	elseif type1 == 'table' or type1 == 'boolean' or type1 == 'function' then
		return tostring(item1) < tostring(item2)
	else
		return item1 < item2
	end
end
------------------------------------------------------------------------------------
-- keysToList
--
-- Returns an array of the keys in a table, sorted using either a default
-- comparison function or a custom keySort function.
------------------------------------------------------------------------------------
function p.keysToList(t, keySort, checked)
	if not checked then
		checkType('keysToList', 1, t, 'table')
		checkTypeMulti('keysToList', 2, keySort, {'function', 'boolean', 'nil'})
	end

	local arr = {}
	local index = 1
	for k in pairs(t) do
		arr[index] = k
		index = index + 1
	end

	if keySort ~= false then
		keySort = type(keySort) == 'function' and keySort or defaultKeySort
		table.sort(arr, keySort)
	end

	return arr
end

------------------------------------------------------------------------------------
-- sortedPairs
--
-- Iterates through a table, with the keys sorted using the keysToList function.
-- If there are only numerical keys, sparseIpairs is probably more efficient.
------------------------------------------------------------------------------------
function p.sortedPairs(t, keySort)
	checkType('sortedPairs', 1, t, 'table')
	checkType('sortedPairs', 2, keySort, 'function', true)

	local arr = p.keysToList(t, keySort, true)

	local i = 0
	return function ()
		i = i + 1
		local key = arr[i]
		if key ~= nil then
			return key, t[key]
		else
			return nil, nil
		end
	end
end

------------------------------------------------------------------------------------
-- isArray
--
-- Returns true if the given value is a table and all keys are consecutive
-- integers starting at 1.
------------------------------------------------------------------------------------
function p.isArray(v)
	if type(v) ~= 'table' then
		return false
	end
	local i = 0
	for _ in pairs(v) do
		i = i + 1
		if v[i] == nil then
			return false
		end
	end
	return true
end

------------------------------------------------------------------------------------
-- isArrayLike
--
-- Returns true if the given value is iterable and all keys are consecutive
-- integers starting at 1.
------------------------------------------------------------------------------------
function p.isArrayLike(v)
	if not pcall(pairs, v) then
		return false
	end
	local i = 0
	for _ in pairs(v) do
		i = i + 1
		if v[i] == nil then
			return false
		end
	end
	return true
end

------------------------------------------------------------------------------------
-- invert
--
-- Transposes the keys and values in an array. For example, {"a", "b", "c"} ->
-- {a = 1, b = 2, c = 3}. Duplicates are not supported (result values refer to
-- the index of the last duplicate) and NaN values are ignored.
------------------------------------------------------------------------------------
function p.invert(arr)
	checkType("invert", 1, arr, "table")
	local isNan = p.isNan
	local map = {}
	for i, v in ipairs(arr) do
		if not isNan(v) then
			map[v] = i
		end
	end

	return map
end

------------------------------------------------------------------------------------
-- listToSet
--
-- Creates a set from the array part of the table. Indexing the set by any of the
-- values of the array returns true. For example, {"a", "b", "c"} ->
-- {a = true, b = true, c = true}. NaN values are ignored as Lua considers them
-- never equal to any value (including other NaNs or even themselves).
------------------------------------------------------------------------------------
function p.listToSet(arr)
	checkType("listToSet", 1, arr, "table")
	local isNan = p.isNan
	local set = {}
	for _, v in ipairs(arr) do
		if not isNan(v) then
			set[v] = true
		end
	end

	return set
end

------------------------------------------------------------------------------------
-- deepCopy
--
-- Recursive deep copy function. Preserves identities of subtables.
------------------------------------------------------------------------------------
local function _deepCopy(orig, includeMetatable, already_seen)
	-- Stores copies of tables indexed by the original table.
	already_seen = already_seen or {}

	local copy = already_seen[orig]
	if copy ~= nil then
		return copy
	end

	if type(orig) == 'table' then
		copy = {}
		for orig_key, orig_value in pairs(orig) do
			copy[_deepCopy(orig_key, includeMetatable, already_seen)] = _deepCopy(orig_value, includeMetatable, already_seen)
		end
		already_seen[orig] = copy

		if includeMetatable then
			local mt = getmetatable(orig)
			if mt ~= nil then
				local mt_copy = _deepCopy(mt, includeMetatable, already_seen)
				setmetatable(copy, mt_copy)
				already_seen[mt] = mt_copy
			end
		end
	else -- number, string, boolean, etc
		copy = orig
	end
	return copy
end

function p.deepCopy(orig, noMetatable, already_seen)
	checkType("deepCopy", 3, already_seen, "table", true)
	return _deepCopy(orig, not noMetatable, already_seen)
end

------------------------------------------------------------------------------------
-- sparseConcat
--
-- Concatenates all values in the table that are indexed by a number, in order.
-- sparseConcat{a, nil, c, d}  =>  "acd"
-- sparseConcat{nil, b, c, d}  =>  "bcd"
------------------------------------------------------------------------------------
function p.sparseConcat(t, sep, i, j)
	local arr = {}

	local arr_i = 0
	for _, v in p.sparseIpairs(t) do
		arr_i = arr_i + 1
		arr[arr_i] = v
	end

	return table.concat(arr, sep, i, j)
end

------------------------------------------------------------------------------------
-- length
--
-- Finds the length of an array, or of a quasi-array with keys such as "data1",
-- "data2", etc., using an exponential search algorithm. It is similar to the
-- operator #, but may return a different value when there are gaps in the array
-- portion of the table. Intended to be used on data loaded with mw.loadData. For
-- other tables, use #.
-- Note: #frame.args in frame object always be set to 0, regardless of  the number
-- of unnamed template parameters, so use this function for frame.args.
------------------------------------------------------------------------------------
function p.length(t, prefix)
	-- requiring module inline so that [[Module:Exponential search]] which is
	-- only needed by this one function doesn't get millions of transclusions
	local expSearch = require("Module:Exponential search")
	checkType('length', 1, t, 'table')
	checkType('length', 2, prefix, 'string', true)
	return expSearch(function (i)
		local key
		if prefix then
			key = prefix .. tostring(i)
		else
			key = i
		end
		return t[key] ~= nil
	end) or 0
end

------------------------------------------------------------------------------------
-- inArray
--
-- Returns true if valueToFind is a member of the array, and false otherwise.
------------------------------------------------------------------------------------
function p.inArray(arr, valueToFind)
	checkType("inArray", 1, arr, "table")
	-- if valueToFind is nil, error?

	for _, v in ipairs(arr) do
		if v == valueToFind then
			return true
		end
	end
	return false
end

return p