Module:TableTools

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

-- <nowiki>
--------------------------------------------------------------------------------
-- This module includes a number of functions for dealing with Lua tables.
--
-- @script TableTools
-- @alias p
-- @release stable
-- @require [[mw:Extension:Scribunto/Lua_reference_manual#libraryUtil|libraryUtil]]
-- @attribution [[wikipedia:Module:TableTools|Module:TableTools]] (Wikipedia)
-- @see [[Wikipedia:Module:TableTools]] for a similar module.
--------------------------------------------------------------------------------
local p = {}
local libraryUtil = require('libraryUtil')
 
-- Define often-used variables and functions.
local floor = math.floor
local infinity = math.huge
local checkType = libraryUtil.checkType

--------------------------------------------------------------------------------
-- Returns a new table with all parameters stored into keys 1, 2, etc. and with
-- a field `n` with the total number of parameters. Note that the resulting
-- table may not be a sequence.
--
-- @function p.pack
-- @param[opt] ...
-- @return {table}
-- @see <http://www.lua.org/manual/5.2/manual.html#pdf-table.pack>
--------------------------------------------------------------------------------
function p.pack(...)
    return {n = select('#', ...), ...}
end

--------------------------------------------------------------------------------
-- Returns the first `n` arguments in `...`. If `n` is negative, arguments are
-- counted from the end of the table.
--
-- @function p.selectFirst
-- @param {number} n
-- @param[opt] ...
-- @see [[Lua reference manual/Standard libraries#select]]
-- @see <http://lua-users.org/wiki/VarargTheSecondClassCitizen>
--------------------------------------------------------------------------------
function p.selectFirst(n, ...)
    checkType('Module:TableTools.selectFirst', 1, n, 'number')

    local function err()
        error('bad argument #1 to \'Module:TableTools.selectFirst\' ' ..
              '(index out of range)')
    end

    local function recurse(index, next, ...)
        if index == 0 then
            return
        end

        return next, recurse(index - 1, ...)
    end

    n = math.modf(n)

    local count = select("#", ...)

    if -count > n then
        err()
    elseif -1 > n and n >= -count then
        return recurse(count + 1 + n, ...)
    elseif n == -1 then
        return ...
    elseif n == 0 then
        err()
    elseif n == 1 then
        return (...)
    elseif 1 < n and n <= count then
        return recurse(n, ...)
    elseif count < n then
        return ...
    end
end

--------------------------------------------------------------------------------
-- Returns `true` if a given table is a sequence.
--
-- @function p.isSequence
-- @param {table} t
-- @return {boolean}
-- @see <http://stackoverflow.com/a/6080274>
--------------------------------------------------------------------------------
function p.isSequence(t)
    checkType('Module:TableTools.isSequence', 1, t, 'table')

    local i = 1

    for _ in pairs(t) do
        if t[i] == nil then
            return false
        end

        i = i + 1
    end

    return true
end

--------------------------------------------------------------------------------
-- Returns the number of elements in a table, even if it is not a sequence.
--
-- @function p.size
-- @param {table} t
-- @return {number}
-- @see <http://stackoverflow.com/a/2705804>
--------------------------------------------------------------------------------
function p.size(t)
    checkType('Module:TableTools.size', 1, t, 'table')

    local i = 0

    for _ in pairs(t) do
        i = i + 1
    end

    return i
end

--------------------------------------------------------------------------------
-- Returns `true` if a given table contains a certain element.
--
-- @function p.includes
-- @param {table} t
-- @param elm
-- @return {boolean}
-- @see <http://stackoverflow.com/q/2282444>
--------------------------------------------------------------------------------
function p.includes(t, elm)
    checkType('Module:TableTools.includes', 1, t, 'table')

    for _, v in pairs(t) do
        if v == elm then
            return true
        end
    end

    return false
end

--------------------------------------------------------------------------------
-- Merges the content of the second table with the content in the first one.
--
-- @function p.merge
-- @param {table} dest
-- @param {table} source
-- @return {table}
-- @see <http://wiki.garrysmod.com/page/table/Merge>
--------------------------------------------------------------------------------
function p.merge(dest, source)
    checkType('Module:TableTools.merge', 1, dest, 'table')
    checkType('Module:TableTools.merge', 2, source, 'table')

    for k, v in pairs(source) do
        if type(v) == 'table' and type(dest[k]) == 'table' then
            -- Don't overwrite one table with another; instead merge them
            -- recurisvely.
            p.merge(dest[k], v)
        else
            dest[k] = v
        end
    end

    return dest
end

------------------------------------------------------------------------------------
-- 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
-- @param v
-- @return {boolean}
------------------------------------------------------------------------------------
function p.isPositiveInteger(v)
	if type(v) == 'number' and v >= 1 and floor(v) == v and v < infinity then
		return true
	else
		return false
	end
end

------------------------------------------------------------------------------------
-- 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
-- @param v
-- @return {boolean}
------------------------------------------------------------------------------------
function p.isNan(v)
	if type(v) == 'number' and tostring(v) == '-nan' then
		return true
	else
		return false
	end
end

------------------------------------------------------------------------------------
-- 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
-- @param {table} t
-- @return {table}
------------------------------------------------------------------------------------
function p.shallowClone(t)
	local ret = {}
	for k, v in pairs(t) do
		ret[k] = v
	end
	return ret
end

------------------------------------------------------------------------------------
-- 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
-- @param {table} t
-- @return {table}
------------------------------------------------------------------------------------
function p.removeDuplicates(t)
	checkType('removeDuplicates', 1, t, 'table')
	local isNan = p.isNan
	local ret, exists = {}, {}
	for i, v in ipairs(t) 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			

------------------------------------------------------------------------------------
-- 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
-- @param {table} t
-- @return {table}
------------------------------------------------------------------------------------
function p.numKeys(t)
	checkType('numKeys', 1, t, 'table')
	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

------------------------------------------------------------------------------------
-- 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
-- @param {table} t
-- @param[opt] {boolean} prefix
-- @param[opt] {boolean} suffix
-- @return {table}
------------------------------------------------------------------------------------
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.
		s = s:gsub('([%(%)%%%.%[%]%*%+%-%?%^%$])', '%%%1')
		return s
	end

	prefix = prefix or ''
	suffix = suffix or ''
	prefix = cleanPattern(prefix)
	suffix = cleanPattern(suffix)
	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

------------------------------------------------------------------------------------
-- 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
-- @param {table} t
-- @param[opt] {boolean} compress
-- @return {table}
------------------------------------------------------------------------------------
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

------------------------------------------------------------------------------------
-- 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
-- @param {table} t
-- @return {table}
------------------------------------------------------------------------------------
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

------------------------------------------------------------------------------------
-- This is an iterator for sparse arrays. It can be used like ipairs, but can
-- handle nil values.
--
-- @function p.sparseIpairs
-- @param {table} t
-- @return {function}
------------------------------------------------------------------------------------
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

return p

-- </nowiki>
-- (Add categories here.)