# Array

An array is an ordered sequence of variables.

In Rivals, you can create arrays with [value1, value2, value3, ...] such as:

hit_noise_names = [

You access like my_array[0] for the first item, my_array[1] for the second, and so on. That can be a bit hard to remember at first. In programming, the first slot is usually index 0.
array_length(array) gets the number of items in the array.

It is usually convenient to access arrays with a for loop (described next), which lets you access each item inside.

You can add items to the end of an array with my_array[array_length(my_array)] = new_value, but be careful. Each time the array grows larger, the language needs to rebuild it, which can become slow. If you're going to be adding values often, then initialize the array with my_array[<maximum number you expect to need>] = noone, which will create empty slots in the array up to that size. Be careful to check if the value is noone when later accessing the array.

Under Construction

Once lists (opens new window) are better tested, describe them here as a good alternative to arrays.

# For Loop

For Loops are the primary way to access the contents of an array. At its simplest, a for loop counts from one number to another, and repeats the code inside it for each value.

// prints each number from 0 to 9 (not 10)
var number_to_count_to = 10
for (var i = 0; i < number_to_count_to; i += 1) {

The for loop updates a counter, i, and repeats a block of code until some condition is met.

The i stands for 'iterator.' Each time the loop runs is an 'iteration.'

There are three parts in the head of the for loop, separated by semicolons.

  • The first is a statement when the loop first starts, usually to set the initial value of the iterator.
  • The second is a boolean expression meaning 'should the loop end now?'
  • The third is a statement run each time the loop finishes, usually updating the iterator.

You most often use a for loop to access each value of an array, by counting through each index, and accessing the value at that index.

var my_array = ["a", "b", "c", "d"]
for (var i = 0; i < array_length(my_array); i += 1) {
    var item = my_array[i]

The Assistant has a way to generate for loops over an array, by typing $foreach <array name>$, such as $foreach my_array$.

(Official Docs (opens new window))

# DS datastructures

You may come across other datastructures, starting with DS_, such as DS_list.

GML provides more powerful datastructures that require great care to use, and are typically not recommended. These structures always require a function call to safely destroy them. There are many ways this can not occur, which will lead to gradual memory issues even after the match ends!

Try to use an array or struct instead.