Arrays

Arrays are a fixed-size sequence of objects. In XDK LIVE, arrays can hold any type:

var array1 : array<int32>;

struct vec2d {
    var x : int32;
    var y : int32;
}
let array2 : array<vec2d>;

Initialization

There are multiple ways to initialize and fill arrays:

let array1 : array<int32> = new array<int32>(size = 10);
let array2 : array<int32> = [1,2,3,4];

Length

XDK LIVE arrays know how long arrays are, unlike C arrays. This allows you to do a lot of things with arrays without knowing their size.

fn sum(a : array<int32>) {
    var result = 0;
    for(var i = 0; i < a.length(); i++) {
      result += a[i];
    }
    return result;
}

The only exception to that is returning arrays. While we try hard to do element size inference, in some cases we fail to correctly infer the size of your array and inform you about it. In that case you need to manually specify the array length:

fn returnsArray(): array<int32> {
  let array1 = new array<int32>(size = 10);
  return array1;
}

Access

You access arrays using the familiar square brackets []:

let array1 = [1,2,3,4,5];
let v1 = array1[1];
array1[2] = v1;

Slices

If you only need to take some parts of your array, you can use slices. A slice of an array is a copy of part of the array. For example, in the following code, array2 contains the values [2, 3]:

let array1 = [1,2,3,4,5];
let array2 = array1[1:3];

You can leave out the upper or lower bound of the slice, or both.

Bounds checks

Whenever you access parts of an array, be it by direct access or slices, we need to do a bounds check. In many cases this doesn’t impart any runtime impact, since we can infer the bounds statically. If we can’t, we generate bounds checks and throw an IndexOutOfBoundsException on failure. See Exceptions for more info.