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{{ | {{used in system}} | ||
{{module rating|protected}} | {{module rating|protected}} | ||
{{lua|Module:Exponential search|noprotcat=yes}} | |||
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. | 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. | ||
| Line 9: | Line 8: | ||
To use any of the functions, first you must load the module. | To use any of the functions, first you must load the module. | ||
< | <syntaxhighlight lang="lua"> | ||
local TableTools = require('Module:TableTools') | local TableTools = require('Module:TableTools') | ||
</ | </syntaxhighlight> | ||
== isPositiveInteger == | == isPositiveInteger == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.isPositiveInteger(value) | TableTools.isPositiveInteger(value) | ||
</ | </syntaxhighlight> | ||
Returns <code>true</code> if <code>''value''</code> is a positive integer, and <code>false</code> 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. | Returns <code>true</code> if <code>''value''</code> is a positive integer, and <code>false</code> 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. | ||
| Line 23: | Line 22: | ||
== isNan == | == isNan == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.isNan(value) | TableTools.isNan(value) | ||
</ | </syntaxhighlight> | ||
Returns <code>true</code> if <code>''value''</code> is a NaN value, and <code>false</code> 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.) | Returns <code>true</code> if <code>''value''</code> is a [[NaN]] value, and <code>false</code> 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 == | == shallowClone == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.shallowClone(t) | TableTools.shallowClone(t) | ||
</ | </syntaxhighlight> | ||
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:Extension:Scribunto/Lua reference manual#mw.clone|mw.clone]] instead. | 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 <code>[[mw:Extension:Scribunto/Lua reference manual#mw.clone|mw.clone]]</code> instead. If you want to make a new table with no shared subtables and without metatables transferred, use <code>[[#deepCopy|deepCopy]]</code> with the <code>noMetatable</code> option. | ||
== removeDuplicates == | == removeDuplicates == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.removeDuplicates(t) | TableTools.removeDuplicates(t) | ||
</ | </syntaxhighlight> | ||
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 <code>nil</code> value. (For arrays containing <code>nil</code> values, you can use [[#compressSparseArray|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 {{code|code={5, 4, 4, 3, 4, 2, 2, 1}|lang=lua}} removeDuplicates will return {{code|code={5, 4, 3, 2, 1}|lang=lua}} | 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 <code>nil</code> value. (For arrays containing <code>nil</code> values, you can use <code>[[#compressSparseArray|compressSparseArray]]</code> 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 {{code|code={5, 4, 4, 3, 4, 2, 2, 1}|lang=lua}} <code>removeDuplicates</code> will return {{code|code={5, 4, 3, 2, 1}|lang=lua}}. | ||
== numKeys == | == numKeys == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.numKeys(t) | TableTools.numKeys(t) | ||
</ | </syntaxhighlight> | ||
Takes a table <code>''t''</code> 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 {{code|code={'foo', nil, 'bar', 'baz', a = 'b'}|lang=lua}}, numKeys will return {{code|code={1, 3, 4}|lang=lua}}. | Takes a table <code>''t''</code> 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 {{code|code={'foo', nil, 'bar', 'baz', a = 'b'}|lang=lua}}, <code>numKeys</code> will return {{code|code={1, 3, 4}|lang=lua}}. | ||
== affixNums == | == affixNums == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.affixNums(t, prefix, suffix) | TableTools.affixNums(t, prefix, suffix) | ||
</ | </syntaxhighlight> | ||
Takes a table <code>''t''</code> and returns an array containing the numbers of keys with the optional prefix <code>''prefix''</code> and the optional suffix <code>''suffix''</code>. For example, for the table {{code|code={a1 = 'foo', a3 = 'bar', a6 = 'baz'}|lang=lua}} and the prefix <code>'a'</code>, affixNums will return {{code|code={1, 3, 6}|lang=lua}}. All characters in <code>''prefix''</code> and <code>''suffix''</code> are interpreted literally. | Takes a table <code>''t''</code> and returns an array containing the numbers of keys with the optional prefix <code>''prefix''</code> and the optional suffix <code>''suffix''</code>. For example, for the table {{code|code={a1 = 'foo', a3 = 'bar', a6 = 'baz'}|lang=lua}} and the prefix <code>'a'</code>, <code>affixNums</code> will return {{code|code={1, 3, 6}|lang=lua}}. All characters in <code>''prefix''</code> and <code>''suffix''</code> are interpreted literally. | ||
== numData == | == numData == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.numData(t, compress) | TableTools.numData(t, compress) | ||
</ | </syntaxhighlight> | ||
Given a table with keys like "foo1", "bar1", "foo2", and "baz2", returns a table of subtables in the format {{code|code={ [1] = {foo = 'text', bar = 'text'}, [2] = {foo = 'text', baz = 'text'} }|lang=lua}}. 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. | Given a table with keys like <code>"foo1"</code>, <code>"bar1"</code>, <code>"foo2"</code>, and <code>"baz2"</code>, returns a table of subtables in the format {{code|code={ [1] = {foo = 'text', bar = 'text'}, [2] = {foo = 'text', baz = 'text'} }|lang=lua}}. Keys that don't end with an integer are stored in a subtable named <code>"other"</code>. The compress option compresses the table so that it can be iterated over with <code>ipairs</code>. | ||
== compressSparseArray == | == compressSparseArray == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.compressSparseArray(t) | TableTools.compressSparseArray(t) | ||
</ | </syntaxhighlight> | ||
Takes an array <code>''t''</code> 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 {{code|code={1, nil, foo = 'bar', 3, 2}|lang=lua}}, compressSparseArray will return {{code|code={1, 3, 2}|lang=lua}}. | Takes an array <code>''t''</code> with one or more nil values, and removes the nil values while preserving the order, so that the array can be safely traversed with <code>ipairs</code>. Any keys that are not positive integers are removed. For example, for the table {{code|code={1, nil, foo = 'bar', 3, 2}|lang=lua}}, <code>compressSparseArray</code> will return {{code|code={1, 3, 2}|lang=lua}}. | ||
== sparseIpairs == | == sparseIpairs == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.sparseIpairs(t) | TableTools.sparseIpairs(t) | ||
</ | </syntaxhighlight> | ||
This is an iterator function for traversing a sparse array <code>''t''</code>. It is similar to [[mw:Extension:Scribunto/Lua reference manual#ipairs|ipairs]], but will continue to iterate until the highest numerical key, whereas ipairs may stop after the first <code>nil</code> value. Any keys that are not positive integers are ignored. | This is an iterator function for traversing a sparse array <code>''t''</code>. It is similar to <code>[[mw:Extension:Scribunto/Lua reference manual#ipairs|ipairs]]</code>, but will continue to iterate until the highest numerical key, whereas <code>ipairs</code> may stop after the first <code>nil</code> value. Any keys that are not positive integers are ignored. | ||
Usually sparseIpairs is used in a generic <code>for</code> loop. | Usually <code>sparseIpairs</code> is used in a generic <code>for</code> loop. | ||
< | <syntaxhighlight lang="lua"> | ||
for i, v in TableTools.sparseIpairs(t) do | for i, v in TableTools.sparseIpairs(t) do | ||
-- code block | -- code block | ||
end | end | ||
</ | </syntaxhighlight> | ||
Note that sparseIpairs uses the [[mw:Extension:Scribunto/Lua reference manual#pairs|pairs]] function in its implementation. Although some table keys appear to be ignored, all table keys are accessed when it is run. | Note that <code>sparseIpairs</code> uses the <code>[[mw:Extension:Scribunto/Lua reference manual#pairs|pairs]]</code> function in its implementation. Although some table keys appear to be ignored, all table keys are accessed when it is run. | ||
== size == | == size == | ||
< | <syntaxhighlight lang="lua"> | ||
TableTools.size(t) | TableTools.size(t) | ||
</ | </syntaxhighlight> | ||
Finds the size of a key/value pair table. For example, for the table {{code|code={foo = 'foo', bar = 'bar'}|lang=lua}}, <code>size</code> will return <code>2</code>. The function will also work on arrays, but for arrays it is more efficient to use the <code>#</code> operator. Note that to find the table size, this function uses the <code>[[mw:Extension:Scribunto/Lua reference manual#pairs|pairs]]</code> function to iterate through all of the table keys. | |||
== keysToList == | == keysToList == | ||
< | |||
TableTools.keysToList(t, keySort) | <syntaxhighlight lang="lua"> | ||
</ | TableTools.keysToList(t, keySort, checked) | ||
Returns a list of the keys in a table, sorted using either a default | </syntaxhighlight> | ||
comparison function or a custom keySort function. | |||
Returns a list of the keys in a table, sorted using either a default comparison function or a custom <code>''keySort''</code> function, which follows the same rules as the <code>comp</code> function supplied to <code>[[mw:Extension:Scribunto/Lua reference manual#table.sort|table.sort]]</code>. If <code>''keySort''</code> is <code>false</code>, no sorting is done. Set <code>''checked''</code> to <code>true</code> to skip the internal type checking. | |||
== sortedPairs == | == sortedPairs == | ||
< | |||
<syntaxhighlight lang="lua"> | |||
TableTools.sortedPairs(t, keySort) | TableTools.sortedPairs(t, keySort) | ||
</ | </syntaxhighlight> | ||
Iterates through a table, with the keys sorted using the keysToList function. | |||
If there are only numerical keys, sparseIpairs is probably more efficient. | Iterates through a table, with the keys sorted using the <code>keysToList</code> function. If there are only numerical keys, <code>sparseIpairs</code> is probably more efficient. | ||
== isArray == | == isArray == | ||
< | |||
TableTools.isArray( | <syntaxhighlight lang="lua"> | ||
</ | TableTools.isArray(value) | ||
Returns true if all keys | </syntaxhighlight> | ||
Returns <code>true</code> if <code>''value''</code> is a table and all keys are consecutive integers starting at 1. | |||
== isArrayLike == | |||
<syntaxhighlight lang="lua"> | |||
TableTools.isArrayLike(value) | |||
</syntaxhighlight> | |||
Returns <code>true</code> if <code>''value''</code> is iterable and all keys are consecutive integers starting at 1. | |||
== invert == | == invert == | ||
< | |||
TableTools.invert( | <syntaxhighlight lang="lua"> | ||
</ | TableTools.invert(arr) | ||
Transposes the keys and values in a table. | </syntaxhighlight> | ||
Transposes the keys and values in an array. For example, {{code|invert{ "a", "b", "c" }|lua}} yields {{code|code={ a=1, b=2, c=3 }|lang=lua}}. | |||
== listToSet == | |||
<syntaxhighlight lang="lua"> | |||
TableTools.listToSet(arr) | |||
</syntaxhighlight> | |||
Creates a set from the array part of the table <code>''arr''</code>. Indexing the set by any of the values of the array returns <code>true</code>. For example, {{code|listToSet{ "a", "b", "c" }|lua}} yields {{code|code={ a=true, b=true, c=true }|lang=lua}}. See also [[Module:Lua set]] for more advanced ways to create a set. | |||
== deepCopy == | == deepCopy == | ||
< | |||
TableTools.deepCopy( | <syntaxhighlight lang="lua"> | ||
</ | TableTools.deepCopy(orig, noMetatable, alreadySeen) | ||
</syntaxhighlight> | |||
Creates a copy of the table <code>''orig''</code>. As with <code>mw.clone</code>, all values that are not functions are duplicated and the identity of tables is preserved. If <code>''noMetatable''</code> is <code>true</code>, then the metatable (if any) is not copied. Can copy tables loaded with <code>mw.loadData</code>. | |||
Similar to <code>mw.clone</code>, but <code>mw.clone</code> cannot copy tables loaded with <code>mw.loadData</code> and does not allow metatables <em>not</em> to be copied. | |||
== sparseConcat == | == sparseConcat == | ||
< | |||
TableTools.sparseConcat(t) | <syntaxhighlight lang="lua"> | ||
</ | TableTools.sparseConcat(t, sep, i, j) | ||
Concatenates all values in the table that are indexed by a | </syntaxhighlight> | ||
Concatenates all values in the table that are indexed by a positive integer, in order. For example, {{code|sparseConcat{ "a", nil, "c", "d" }|lua}} yields {{code|"acd"|lua}} and {{code|sparseConcat{ nil, "b", "c", "d" }|lua}} yields {{code|"bcd"|lua}}. | |||
== length == | == length == | ||
< | |||
TableTools.length(t) | <syntaxhighlight lang="lua"> | ||
</ | TableTools.length(t, prefix) | ||
</syntaxhighlight> | |||
Finds the length of an array or of a quasi-array with keys with an optional <code>''prefix''</code> 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. [[mw:Extension:Scribunto/Lua reference manual#frame.args|frame.args]]) and for quasi-arrays. For normal arrays, just use the [[mw:Extension:Scribunto/Lua reference manual#Length operator|# operator]], as it is implemented in [[C (programming language)|C]] and will be quicker. | |||
== inArray == | == inArray == | ||
< | |||
TableTools.inArray(arr,valueToFind) | <syntaxhighlight lang="lua"> | ||
</ | TableTools.inArray(arr, valueToFind) | ||
Returns < | </syntaxhighlight> | ||
Returns <code>true</code> if <code>''valueToFind''</code> is a member of the array <code>''arr''</code>, and <code>false</code> otherwise. | |||
<includeonly>{{Sandbox other|| | <includeonly>{{Sandbox other|| | ||
[[Category:Lua metamodules|TableTools]] | [[Category:Lua metamodules|TableTools]] | ||
}}</includeonly> | }}</includeonly> | ||
Latest revision as of 03:37, 15 September 2023
| Warning | This Lua module is used in system messages, and on approximately 6,140,000 pages, or roughly 143157% 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. |
| File:Lua-Logo.svg | This module depends on the following other modules: |
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.
<syntaxhighlight lang="lua"> local TableTools = require('Module:TableTools') </syntaxhighlight>
isPositiveInteger
<syntaxhighlight lang="lua"> TableTools.isPositiveInteger(value) </syntaxhighlight>
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
<syntaxhighlight lang="lua"> TableTools.isNan(value) </syntaxhighlight>
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
<syntaxhighlight lang="lua"> TableTools.shallowClone(t) </syntaxhighlight>
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
<syntaxhighlight lang="lua"> TableTools.removeDuplicates(t) </syntaxhighlight>
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 <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{5, 4, 4, 3, 4, 2, 2, 1}</syntaxhighlight> removeDuplicates will return <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{5, 4, 3, 2, 1}</syntaxhighlight>.
numKeys
<syntaxhighlight lang="lua"> TableTools.numKeys(t) </syntaxhighlight>
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 <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{'foo', nil, 'bar', 'baz', a = 'b'}</syntaxhighlight>, numKeys will return <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{1, 3, 4}</syntaxhighlight>.
affixNums
<syntaxhighlight lang="lua"> TableTools.affixNums(t, prefix, suffix) </syntaxhighlight>
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 <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{a1 = 'foo', a3 = 'bar', a6 = 'baz'}</syntaxhighlight> and the prefix 'a', affixNums will return <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{1, 3, 6}</syntaxhighlight>. All characters in prefix and suffix are interpreted literally.
numData
<syntaxhighlight lang="lua"> TableTools.numData(t, compress) </syntaxhighlight>
Given a table with keys like "foo1", "bar1", "foo2", and "baz2", returns a table of subtables in the format <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{ [1] = {foo = 'text', bar = 'text'}, [2] = {foo = 'text', baz = 'text'} }</syntaxhighlight>. 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
<syntaxhighlight lang="lua"> TableTools.compressSparseArray(t) </syntaxhighlight>
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 <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{1, nil, foo = 'bar', 3, 2}</syntaxhighlight>, compressSparseArray will return <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{1, 3, 2}</syntaxhighlight>.
sparseIpairs
<syntaxhighlight lang="lua"> TableTools.sparseIpairs(t) </syntaxhighlight>
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.
<syntaxhighlight lang="lua"> for i, v in TableTools.sparseIpairs(t) do
-- code block
end </syntaxhighlight>
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
<syntaxhighlight lang="lua"> TableTools.size(t) </syntaxhighlight>
Finds the size of a key/value pair table. For example, for the table <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{foo = 'foo', bar = 'bar'}</syntaxhighlight>, 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
<syntaxhighlight lang="lua"> TableTools.keysToList(t, keySort, checked) </syntaxhighlight>
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
<syntaxhighlight lang="lua"> TableTools.sortedPairs(t, keySort) </syntaxhighlight>
Iterates through a table, with the keys sorted using the keysToList function. If there are only numerical keys, sparseIpairs is probably more efficient.
isArray
<syntaxhighlight lang="lua"> TableTools.isArray(value) </syntaxhighlight>
Returns true if value is a table and all keys are consecutive integers starting at 1.
isArrayLike
<syntaxhighlight lang="lua"> TableTools.isArrayLike(value) </syntaxhighlight>
Returns true if value is iterable and all keys are consecutive integers starting at 1.
invert
<syntaxhighlight lang="lua"> TableTools.invert(arr) </syntaxhighlight>
Transposes the keys and values in an array. For example, <syntaxhighlight lang="lua" class="" id="" style="" inline="1">invert{ "a", "b", "c" }</syntaxhighlight> yields <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{ a=1, b=2, c=3 }</syntaxhighlight>.
listToSet
<syntaxhighlight lang="lua"> TableTools.listToSet(arr) </syntaxhighlight>
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, <syntaxhighlight lang="lua" class="" id="" style="" inline="1">listToSet{ "a", "b", "c" }</syntaxhighlight> yields <syntaxhighlight lang="lua" class="" id="" style="" inline="1">{ a=true, b=true, c=true }</syntaxhighlight>. See also Module:Lua set for more advanced ways to create a set.
deepCopy
<syntaxhighlight lang="lua"> TableTools.deepCopy(orig, noMetatable, alreadySeen) </syntaxhighlight>
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
<syntaxhighlight lang="lua"> TableTools.sparseConcat(t, sep, i, j) </syntaxhighlight>
Concatenates all values in the table that are indexed by a positive integer, in order. For example, <syntaxhighlight lang="lua" class="" id="" style="" inline="1">sparseConcat{ "a", nil, "c", "d" }</syntaxhighlight> yields <syntaxhighlight lang="lua" class="" id="" style="" inline="1">"acd"</syntaxhighlight> and <syntaxhighlight lang="lua" class="" id="" style="" inline="1">sparseConcat{ nil, "b", "c", "d" }</syntaxhighlight> yields <syntaxhighlight lang="lua" class="" id="" style="" inline="1">"bcd"</syntaxhighlight>.
length
<syntaxhighlight lang="lua"> TableTools.length(t, prefix) </syntaxhighlight>
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
<syntaxhighlight lang="lua"> TableTools.inArray(arr, valueToFind) </syntaxhighlight>
Returns true if valueToFind is a member of the array arr, and false otherwise.