But strictly speaking, there's no such thing as an array in Lua. Many languages call this an array, and so will we. We're using this table as a sequence: a group of items keyed by integers. For example: - Create a table to store the types of pets we like. Avoiding gaps in tables used as arrays Defining our termsīy array here we mean a Lua table used as a sequence. It uses the table.insert() to append the randomly extracted element onto the end of same table, and the table.remove() to randomly extract an element from the remaining unshuffled portion of the table. It implements the Fisher-Yates Shuffle, perhaps inefficiently. Table.insert(t, table.remove(t, math.random(#t-i))) Leveraging that, you can write code like the example below. As you might be able to tell the second method of calling table.insert() and table.remove() provides stack semantics to tables. These two functions mutate the given table. Creating tablesĬreating an empty table is as simple as this: local empty_table =, r = 'e' When coding for a table with a sequence, it is important to avoid breaking the sequence Only remove the last element or use a function, like the standard table.remove, that shifts elements down to close the gap. Iterators would no longer see the related key. Setting a value in a table to nil removes it from the table. Certain standard operations and functions only work on the sequence of a table and some have non-deterministic behavior when applied to a table without a sequence. Other languages call this a 1-based array. The key-value pairs with positive integer keys are the elements of the sequence. So, for example, one table could contain strings, functions, booleans, numbers, and even other tables as values or keys.Ī Lua table with consecutive positive integer keys beginning with 1 is said to have a sequence. The items contained in a table can be a mixture of Lua types.

Lua does not enforce any particular rules on how tables are used. Finally, tables can be used to build classes in Lua and to create a module system. Many structural patterns can be built with tables: stacks, queues, sets, lists, graphs, etc. As such, a Lua table can resemble a dictionary, hashmap or associative array from other languages.

This is either elegant simplicity or confusing, depending on how you look at it.Ī Lua table is a collection of key-value pairs where the keys are unique and neither the key nor the value is nil. Tables are the only built-in data structure available in Lua.

Lua table insert and remove