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In Lua, "table" is a fundamental type that can be used either as an array (numerical index, fast) or as an associative array. The keys and values can be of any type, except nil. The following focuses on non-numerical indexes. A table literal is written as { value, key = value, [index] = value, ["non id string"] = value }. For example:
In addition to support for vectorized arithmetic and relational operations, these languages also vectorize common mathematical functions such as sine. For example, if x is an array, then y = sin (x) will result in an array y whose elements are sine of the corresponding elements of the array x. Vectorized index operations are also supported.
The most frequently used general-purpose implementation of an associative array is with a hash table: an array combined with a hash function that separates each key into a separate "bucket" of the array. The basic idea behind a hash table is that accessing an element of an array via its index is a simple, constant-time operation.
A table is a sequence, optionally supplemented by named keys: digit["two"]="2". Several table functions like table.concat will only work with the numbered values and ignore named keys. The metatable offers a large, optional set of methods for altering table behavior. For example, you can define a table to be callable like a function.
R (array, interpreted, impure, interactive mode, list-based, object-oriented prototype-based, scripting) Racket (functional, imperative, object-oriented (class-based) and can be extended by the user) Raku (concurrent, concatenative, functional, metaprogramming generic, imperative, reflection object-oriented, pipelines, reactive, and via ...
# is the length operator for tables and strings. array [0] = "z"-- Zero is a legal index. print (# array)-- Still prints 4, as Lua arrays are 1-based. The length of a table t is defined to be any integer index n such that t[n] is not nil and t[n+1] is nil ; moreover, if t[1] is nil , n can be zero.
Because of this, many formulas in algorithms (such as that for calculating hash table indices) can be elegantly expressed in code using the modulo operation when array indices start at zero. Pointer operations can also be expressed more elegantly on a zero-based index due to the underlying address/offset logic mentioned above.
Lua functions may pass varargs to other functions the same way as other values using the return keyword. tables can be passed into variadic functions by using, in Lua version 5.2 or higher [9] table.unpack, or Lua 5.1 or lower [10] unpack. Varargs can be used as a table by constructing a table with the vararg as a value.