arrays

Arrays

You can create arrays in cairo with ArrayTrait::new() and add elements with the method append:

use array::ArrayTrait;

fn get_array() -> Array<felt252> {
    let mut numbers = ArrayTrait::new();
    numbers.append(444);
    numbers.append(555);

    numbers
}

You can get the length of an array with len:

#[test]
fn test_array_len() {
    let array = get_array();
    let len = array.len();
    assert(len == 2, 'wrong array length');
}

You can get an element from an array with get or at:

#[test]
fn test_array_get() {
    let array = get_array();
    let first_element = *array.get(0).unwrap().unbox();
    let second_element = *array.at(1);

    assert(first_element == 444, 'wrong first element');
    assert(second_element == 555, 'wrong second element');
}

The difference between get and at is that at will cause an error if there is no element at the specified index while get returns an Option that is None in that case.

Full example:

use array::ArrayTrait;
use option::OptionTrait;
use box::BoxTrait;

fn get_array() -> Array<felt252> {
    let mut numbers = ArrayTrait::new();
    numbers.append(444);
    numbers.append(555);

    numbers
}

#[test]
fn test_array_len() {
    let array = get_array();
    let len = array.len();

    assert(len == 2, 'wrong array length');
}

#[test]
fn test_array_retrieve_elements() {
    let array = get_array();
    let first_element = *array.get(0).unwrap().unbox();
    let second_element = *array.at(1);

    assert(first_element == 444, 'wrong first element');
    assert(second_element == 555, 'wrong second element');

    // array.get(2) will return None
    // array.at(2) will cause an error
}

Try it out!

Install the toolchain:

For macOS and Linux, run our script:

curl -sL https://raw.githubusercontent.com/lambdaclass/cairo-by-example/main/build/installer.sh | bash -s 2.2.0

For Windows and others, please see the official guide

Run the example:
1. Copy the example into a arrays.cairo file and run with:

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arrays

Arrays