Module:TableTools/doc
This is a documentation subpage for Module:TableTools. It may contain usage information, categories and other content that is not part of the original module page. |
This Lua module is used on approximately 6,250,000 pages, or roughly 10% of all pages. To avoid major disruption and server load, any changes should be tested in the module's /sandbox or /testcases subpages, or in your own module sandbox. The tested changes can be added to this page in a single edit. Consider discussing changes on the talk page before implementing them. |
This Lua module is used in system messages, and on approximately 6,250,000 pages, or roughly 10% of all pages. Changes to it can cause immediate changes to the Wikipedia user interface. To avoid major disruption and server load, any changes should be tested in the module's /sandbox or /testcases subpages, or in your own module sandbox. The tested changes can be added to this page in a single edit. Please discuss changes on the talk page before implementing them. |
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)
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
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)
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
TableTools.inArray(arr, valueToFind)
Returns true
if valueToFind
is a member of the array arr
, and false
otherwise.