Programming in Lua : 11.1

Part II. Tables and Objects Chapter 11. Data Structures

11.1 - Arrays

We implement arrays in Lua simply by indexing tables with integers. Therefore, arrays do not have a fixed size, but grow as we need. Usually, when we initialize the array we define its size indirectly. For instance, after the following code

    a = {}    -- new array
    for i=1, 1000 do
      a[i] = 0
    end

any attempt to access a field outside the range 1-1000 will return nil, instead of zero.

You can start an array at index 0, 1, or any other value:

    -- creates an array with indices from -5 to 5
    a = {}
    for i=-5, 5 do
      a[i] = 0
    end

However, it is customary in Lua to start arrays with index 1. The Lua libraries adhere to this convention; so, if your arrays also start with 1, you will be able to use their functions directly.

We can use constructors to create and initialize arrays in a single expression:

    squares = {1, 4, 9, 16, 25, 36, 49, 64, 81}

Such constructors can be as large as you need (well, up to a few million elements).