Module: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.

Loading the module

To use any of the functions, first you must load the module.

<syntaxhighlight lang="lua"> local TableTools = require('Module:TableTools') </syntaxhighlight>

isPositiveInteger

<syntaxhighlight lang="lua"> TableTools.isPositiveInteger(value) </syntaxhighlight>

Returns true if 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.

isNan

<syntaxhighlight lang="lua"> TableTools.isNan(value) </syntaxhighlight>

Returns true if value 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 value is used as a table key.)

shallowClone

<syntaxhighlight lang="lua"> TableTools.shallowClone(t) </syntaxhighlight>

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. If you want to make a new table with no shared subtables and with metatables transferred, you can use mw.clone instead. If you want to make a new table with no shared subtables and without metatables transferred, use deepCopy with the noMetatable option.

removeDuplicates

<syntaxhighlight lang="lua"> TableTools.removeDuplicates(t) </syntaxhighlight>

Removes duplicate values from an array. This function is only designed to work with standard arrays: keys that are not positive integers are ignored, as are all values after the first nil value. (For arrays containing nil values, you can use compressSparseArray first.) The function tries to preserve the order of the array: the earliest non-unique value is kept, and all subsequent duplicate values are removed. For example, for the table {5, 4, 4, 3, 4, 2, 2, 1} removeDuplicates will return {5, 4, 3, 2, 1}

numKeys

<syntaxhighlight lang="lua"> TableTools.numKeys(t) </syntaxhighlight>

Takes a table t and returns an array containing the numbers of any positive integer keys that have non-nil values, sorted in numerical order. For example, for the table {'foo', nil, 'bar', 'baz', a = 'b'}, numKeys will return {1, 3, 4}.

affixNums

<syntaxhighlight lang="lua"> TableTools.affixNums(t, prefix, suffix) </syntaxhighlight>

Takes a table t and returns an array containing the numbers of keys with the optional prefix prefix and the optional suffix suffix. For example, for the table {a1 = 'foo', a3 = 'bar', a6 = 'baz'} and the prefix 'a', affixNums will return {1, 3, 6}. All characters in prefix and suffix are interpreted literally.

numData

<syntaxhighlight lang="lua"> TableTools.numData(t, compress) </syntaxhighlight>

Given a table with keys like "foo1", "bar1", "foo2", and "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.

compressSparseArray

<syntaxhighlight lang="lua"> TableTools.compressSparseArray(t) </syntaxhighlight>

Takes an array t 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. Any keys that are not positive integers are removed. For example, for the table {1, nil, foo = 'bar', 3, 2}, compressSparseArray will return {1, 3, 2}.

sparseIpairs

<syntaxhighlight lang="lua"> TableTools.sparseIpairs(t) </syntaxhighlight>

This is an iterator function for traversing a sparse array t. It is similar to ipairs, but will continue to iterate until the highest numerical key, whereas ipairs may stop after the first nil value. Any keys that are not positive integers are ignored.

Usually sparseIpairs is used in a generic for loop.

<syntaxhighlight lang="lua"> for i, v in TableTools.sparseIpairs(t) do

  -- code block

end </syntaxhighlight>

Note that sparseIpairs uses the pairs function in its implementation. Although some table keys appear to be ignored, all table keys are accessed when it is run.

size

<syntaxhighlight lang="lua"> TableTools.size(t) </syntaxhighlight>

Finds the size of a key/value pair table. For example, for the table {foo = 'foo', bar = 'bar'}, size will return 2. The function will also work on arrays, but for arrays it is more efficient to use the # operator. Note that to find the table size, this function uses the pairs function to iterate through all of the table keys.

keysToList

<syntaxhighlight lang="lua"> TableTools.keysToList(t, keySort) </syntaxhighlight>

Returns a list of the keys in a table, sorted using either a default comparison function or a custom keySort function, which follows the same rules as the comp function supplied to table.sort.

sortedPairs

<syntaxhighlight lang="lua"> TableTools.sortedPairs(t, keySort) </syntaxhighlight>

Iterates through a table, with the keys sorted using the keysToList function. If there are only numerical keys, sparseIpairs is probably more efficient.

isArray

<syntaxhighlight lang="lua"> TableTools.isArray(t) </syntaxhighlight>

Returns true if all keys in the table are consecutive integers starting at 1.

listToSet

<syntaxhighlight lang="lua"> TableTools.listToSet(arr) </syntaxhighlight>

Creates a set from the array part of the table arr. Indexing the set by any of the values in arr returns true.

<syntaxhighlight lang="lua"> local set = TableTools.listToSet { "a", "b", "c" } assert(set["a"] == true) </syntaxhighlight>

invert

<syntaxhighlight lang="lua"> TableTools.invert(t) </syntaxhighlight>

Transposes the keys and values in an array. For example, invert{ "a", "b", "c" } yields { a = 1, b = 2, c = 3 }.

deepCopy

<syntaxhighlight lang="lua"> TableTools.deepCopy(orig, noMetatable, alreadySeen) </syntaxhighlight>

Creates a copy of the table orig. As with mw.clone, all values that are not functions are duplicated and the identity of tables is preserved. If noMetatable is true, then the metatable (if any) is not copied. Can copy tables loaded with mw.loadData.

Similar to mw.clone, but mw.clone cannot copy tables loaded with mw.loadData and does not allow metatables not to be copied.

sparseConcat

<syntaxhighlight lang="lua"> TableTools.sparseConcat(t, sep) </syntaxhighlight>

Concatenates all values in the table that are indexed by a positive integer, in order.

length

<syntaxhighlight lang="lua"> TableTools.length(t) </syntaxhighlight>

Finds the length of an array, or of a quasi-array with keys such as "data1", "data2", etc. It uses a binary search algorithm to find the length, so as to use as few table lookups as possible.

This algorithm is useful for arrays that use metatables (e.g. frame.args) and for quasi-arrays. For normal arrays, just use the # operator, as it is implemented in C and will be quicker.

inArray

<syntaxhighlight lang="lua"> TableTools.inArray(arr, valueToFind) </syntaxhighlight>

Returns <syntaxhighlight lang="lua" inline>true</syntaxhighlight> if valueToFind is a member of the array arr, and <syntaxhighlight lang="lua" inline>false</syntaxhighlight> otherwise.

---

--[[
------------------------------------------------------------------------------------
--                               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 p = {}

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

-- Define a unique value to represent NaN. This is because NaN cannot be used as a table key.
local nan = {}

--[[
------------------------------------------------------------------------------------
-- isPositiveInteger
--
-- This function returns true if the given number 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(num)
	if type(num) == 'number' and num >= 1 and floor(num) == num and num < infinity then
		return true
	else
		return false
	end
end

--[[
------------------------------------------------------------------------------------
-- union
--
-- This returns the union of the values of n tables, as an array. For example, for
-- the tables {1, 3, 4, 5, foo = 7} and {2, bar = 3, 5, 6}, union will return
-- {1, 2, 3, 4, 5, 6, 7}.
------------------------------------------------------------------------------------
--]]
function p.union(...)
	local vals, ret = {}, {}
	for i = 1, select('#', ...) do
		local t = select(i, ...)
		for k, v in pairs(t) do
			if type(v) == 'number' and tostring(v) == '-nan' then
				v = nan -- NaN cannot be a table key, so use a proxy variable.
			end
			vals[v] = true
		end
	end
	for val in pairs(vals) do
		if val == nan then
			-- This ensures that we output a NaN when we had one as input, although
			-- they may have been generated in a completely different way.
			val = 0/0 
		end
		ret[#ret + 1] = val
	end
	return ret
end	

--[[
------------------------------------------------------------------------------------
-- intersection
--
-- This returns the intersection of the values of n tables, as an array. For
-- example, for the tables {1, 3, 4, 5, foo = 7} and {2, bar = 3, 5, 6}, 
-- intersection will return {3, 5}.
------------------------------------------------------------------------------------
--]]
function p.intersection(...)
	local vals, ret = {}, {}
	local lim = select('#', ...)
	for i = 1, lim do
		local t = select(i, ...)
		for k, v in pairs(t) do
			if type(v) == 'number' and tostring(v) == '-nan' then
				v = nan -- NaN cannot be a table key, so use a proxy variable.
			end
			local valCount = vals[v] or 0
			vals[v] = valCount + 1
		end
	end
	for val, count in pairs(vals) do
		if count == lim then
			if val == nan then
				-- This ensures that we output a NaN when we had one as input, although
				-- they may have been generated in a completely different way.
				val = 0/0 
			end
			ret[#ret + 1] = val
		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)
	local isPositiveInteger = p.isPositiveInteger
	local nums = {}
	for k, v 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)
	prefix = prefix or ''
	suffix = suffix or ''
	local pattern = '^' .. prefix .. '([1-9]%d*)' .. suffix .. '$'
	local nums = {}
	for k, v 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

--[[
------------------------------------------------------------------------------------
-- 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)
	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)
	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]
		end
	end
end

return p