Lesson 7 of 11
Vectors and indexing
Build a growable list and check whether an item exists.
main.rs
fn main() { let mut scores = vec![10, 20]; scores.push(30); println!("First: {}", scores[0]); println!("Index 2: {:?}", scores.get(2)); println!("Index 8: {:?}", scores.get(8));}Program state
- scores
- Uninitialized
Step 1 of 6
The program will create a list of scores.
What’s happening
A vector stores an ordered list of values of one type. The vec! macro creates a vector from the values you supply. Use push on a mutable vector to append an item.
Indexes start at zero. Use brackets when you know the index exists. Indexing outside the vector panics. The get method returns Some with a reference to an item, or None if the index is out of bounds.
The {:?} placeholder shows the result's debug representation, so you can see the Some and None cases directly.
Read more in The Rust Book