Array

An Array is an ordered collection of values.

Creating arrays

An array can be created by using brackets:

let myArr = []; // An empty array

You can also initialize an array with values:

let myArr = [ 2, 5 + 5, "a string", true, null ];

Reading values

You can access an Array's index by using the array access operator []:

let myArr = [ 1, "a string", 2 ];

io.print(myArr[0]); // 1

io.print(myArr[1]); // a string

io.print(myArr[2]); // 2

note

If you access an index that's past the end of the array an error will be triggered. This is somewhat different from popular dynamic languages, but is done intentionally to avoid undetected bugs. Melon can do this because arrays are a completely different type from Object and share nothing with it, while other popular programming languages use the equivalent of Object for arrays or an extension thereof.

Reading size

You can use the size operator # to retrieve an Array's size:

io.print(#[]); // 0

io.print(#[1, 2, 3]); // 3

Adding values

You can add values to an existing array by not passing an index to the array access operator [] as follows:

let myArr = [];

myArr[] = 1;

myArr[] = 2;

io.print(#myArr); // 2

Writing values

Writing values to existing array indices works as you would expect:

let myArr = [ null ];

io.print(myArr[0]); // null

myArr[0] = "it works";

io.print(myArr[0]); // it works

Iterating

Arrays provide a native Iterator that can be used to iterate over them:

let fruits = [ "banana", "mango", "melon" ];

for (let fruit in fruits) {

io.print(fruit);

}

Outputs:

banana

mango

melon

You can also iterate over arrays using Range values, for example because the index of the item is needed:

let fruits = [ "banana", "mango", "melon" ];

for (let i in 0..#fruits) {

io.print(i, fruits[i]);

}

Outputs:

0 banana

1 mango

2 melon

Array slicing

Array values can be sliced returning a new array composed of only a part of the original. The slicing operator [start:end] can be used for slicing. The start index is inclusive and the end index is exclusive. Both the start and end index are optional and the end index can also be a negative index expressing an index starting from the end of the array.

let myArrWhole = [1, 2, 3, 4];

let myArrA = myArrWhole[1:]; // [2, 3, 4];

let myArrB = myArrWhole[:2]; // [1, 2];

let myArrC = myArrWhole[1:-1]; // [2, 3];

You can use the slicing operator to clone an Array value:

let myArrWhole = [1, 2, 3, 4];

let myArrCopy = myArrWhole[:];

io.print(#myArrWhole == #myArrCopy); // true

io.print(myArrCopy == myArrWhole); // false

Concatenation

You can combine two arrays in a new array by using the concatenation operator ..:

let myArrA = [ "banana", "mango" ];

let myArrB = [ "melon" ];

let myArrC = myArrA .. myArrB; // banana, mango, melon

let myArrD = myArrB .. myArrA; // melon, mango, banana

Further array manipulation

There are other ways to manipulate Array values, they can be found in the array core module.