Function Dump/Table Manipulation

Up one category: Function Dump

Table Manipulation

This library provides generic functions for table manipulation. It provides all its functions inside the table table.

Most functions in the table library assume that the table represents an array or a list. For these functions, when we talk about the "length" of a table we mean the result of the length operator.

table.concat (table [, sep [, i [, j]]])

Given an array where all elements are strings or numbers, returns table[i]..sep..table[i+1] ··· sep..table[j]. The default value for sep is the empty string, the default for i is 1, and the default for j is the length of the table. If i is greater than j, returns the empty string.

Example:

t = { "I", "like", "to", "play", "GoodBlox" }
print (table.concat (t, ' '))

Will result in:
I like to play GoodBlox

table.foreach (table, f)

Applies the function f to the elements of the table passed. On each iteration the function f is passed the key-value pair of that element in the table. This item is deprecated; use the pairs() operator instead![1]

Example:

t = { "I", "like", "to", "play", game = "GoodBlox" }
table.foreach (t, print)

Will result in:
1 I
2 like
3 to
4 play
game GoodBlox

table.foreachi(table, f)

Applies the function f to the elements of the table passed. On each iteration the function f is passed the index-value pair of that element in the table. This is similar to table.foreach() except that index-value pairs are passed, not key-value pairs. If the function f returns a non-nil value the iteration loop terminates. This item is deprecated; use the ipairs() operator instead![2]

Example:

t = { "I", "like", "to", "play", game = "GoodBlox" }
table.foreachi (t, print)

Will result in:
1 I
2 like
3 to
4 play

Similar to table.foreach, except that only numeric keys in the range 1 to n are processed. In this example the entry for "game = 'GoodBlox'" was not returned because it did not have a numeric key.[3]

table.getn (table)

Returns the size of the table, when seen as a list. This item is deprecated; use the '#' operator instead!

Example:

a=table.getn { "I", "like", "to", "play", game="GoodBlox"}
print(a)

Will result in:
4

table.insert (table, [pos,] value)

Inserts element value at position pos in table, shifting up other elements to open space, if necessary. The default value for pos is n+1, where n is the length of the table (see §2.5.5), so that a call table.insert(t,x) inserts x at the end of table t.

Example:

t = { "I", "like", "to", "play", "GoodBlox" }
table.insert (t, 2, "do")
table.insert (t, 3, "not")
print (table.concat (t, ' '))

Will result in:
I do not like to play GoodBlox

table.maxn (table)

Returns the largest positive numerical index of the given table, or zero if the table has no positive numerical indices. (To do its job this function does a linear traversal of the whole table.)[4]

Example:

numbers = {0, 1, 2, 3, 4, 5, 6}
print(table.maxn (numbers))

Will result in:
7

table.remove (table [, pos])

Removes from table the element at position pos, shifting down other elements to close the space, if necessary. Returns the value of the removed element. The default value for pos is n, where n is the length of the table, so that a call table.remove(t) removes the last element of table t.

Example:

numbers = {0, 1, 2, 3, 4, 5, 6}
print (numbers[4])
table.remove (numbers, 4)
print (numbers[4])

Will result in:
3 4

table.setn (t, n)

This has been removed from Lua 5.1. Attempting to call it will raise an error. The length of a table can not be set, it is implied by the highest numeric key, providing there are no gaps in the sequence of numeric keys.[5]

Example:

table.setn({})

Will result in:
'setn' is obsolete

table.sort (table [, comp])

Sorts table elements in a given order, in-place, from table[1] to table[n], where n is the length of the table. If comp is given, then it must be a function that receives two table elements, and returns true when the first is less than the second (so that not comp(a[i+1],a[i]) will be true after the sort). If comp is not given, then the standard Lua operator < is used instead.

The sort algorithm is not stable; that is, elements considered equal by the given order may have their relative positions changed by the sort.

Example:

t = { "I", "like", "to", "play", "GoodBlox" }
table.sort (t)
print (table.concat (t, ' '))

Will result in:
I GoodBlox like play to