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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')

Functions

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)

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 Template:Ll.

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(t)

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

listToSet

TableTools.listToSet(arr)

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

local set = TableTools.listToSet { "a", "b", "c" }
assert(set["a"] === true)

invert

TableTools.invert(t)

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

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)

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

length

TableTools.length(t)

Returns the length of a table, or the first integer key n counting from 0 such that t[n + 1] is nil. 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 and on frame.args. Both use a metatable such that #mw.loadData("module:...") and #frame.args don't work correctly. For other tables, use #.

inArray

TableTools.inArray(arr, valueToFind)

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