This is the documentation page for 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.
local TableTools = require('Module:TableTools')
isPositiveInteger
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
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
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
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
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
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
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
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
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
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
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
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
TableTools.isArray(value)
Returns true if value is a table and all keys are consecutive integers starting at 1.
isArrayLike
TableTools.isArrayLike(value)
Returns true if value is iterable and all keys are consecutive integers starting at 1.
invert
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
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
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
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
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
TableTools.inArray(arr, valueToFind)
Returns true if valueToFind is a member of the array arr, and false otherwise.
Attribution and re-use
This module (along with its documentation page) has been adapted from Wikipedia released under the Creative Commons Attribution-ShareAlike License 4.0.