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    Farthest Frontier

    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[edit source]

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

    local TableTools = require('Module:TableTools')
    

    isPositiveInteger[edit source]

    TableTools.isPositiveInteger(value)
    

    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[edit source]

    TableTools.isNan(value)
    

    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[edit source]

    TableTools.shallowClone(t)
    

    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[edit source]

    TableTools.removeDuplicates(t)
    

    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[edit source]

    TableTools.numKeys(t)
    

    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[edit source]

    TableTools.affixNums(t, prefix, suffix)
    

    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[edit source]

    TableTools.numData(t, compress)
    

    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[edit source]

    TableTools.compressSparseArray(t)
    

    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[edit source]

    TableTools.sparseIpairs(t)
    

    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.

    for i, v in TableTools.sparseIpairs(t) do
       -- code block
    end
    

    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[edit source]

    TableTools.size(t)
    

    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[edit source]

    TableTools.keysToList(t, keySort, checked)
    

    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. If keySort is false, no sorting is done. Set checked to true to skip the internal type checking.

    sortedPairs[edit source]

    TableTools.sortedPairs(t, keySort)
    

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

    isArray[edit source]

    TableTools.isArray(value)
    

    Returns true if value is a table and all keys are consecutive integers starting at 1.

    isArrayLike[edit source]

    TableTools.isArrayLike(value)
    

    Returns true if value is iterable and all keys are consecutive integers starting at 1.

    invert[edit source]

    TableTools.invert(arr)
    

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

    listToSet[edit source]

    TableTools.listToSet(arr)
    

    Creates a set from the array part of the table arr. Indexing the set by any of the values of the array returns true. For example, listToSet{ "a", "b", "c" } yields { a=true, b=true, c=true }. See also Module:Lua set for more advanced ways to create a set.

    deepCopy[edit source]

    TableTools.deepCopy(orig, noMetatable, alreadySeen)
    

    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[edit source]

    TableTools.sparseConcat(t, sep, i, j)
    

    Concatenates all values in the table that are indexed by a positive integer, in order. For example, sparseConcat{ "a", nil, "c", "d" } yields "acd" and sparseConcat{ nil, "b", "c", "d" } yields "bcd".

    length[edit source]

    TableTools.length(t, prefix)
    

    Finds the length of an array or of a quasi-array with keys with an optional prefix such as "data1", "data2", etc. It uses an exponential 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[edit source]

    TableTools.inArray(arr, valueToFind)
    

    Returns true if valueToFind is a member of the array arr, and false 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 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
    
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