Array
The type of array is [T; Lengh]
, as you can see, array's lengh is part of their type signature. So their length must be known at compile time.
For example, you cant initialized an array as below:
#![allow(unused)] fn main() { fn init_arr(n: i32) { let arr = [1; n]; } }
This will cause an error, because the compile have no idea of the exact size of the array in compile time.
- 🌟
fn main() { // fill the blank with proper array type let arr: __ = [1, 2, 3, 4, 5]; // modify below to make it work assert!(arr.len() == 4); println!("Success!") }
- 🌟🌟
fn main() { // we can ignore parts of the array type or even the whole type, let the compiler infer it for us let arr0 = [1, 2, 3]; let arr: [_; 3] = ['a', 'b', 'c']; // fill the blank // Arrays are stack allocated, `std::mem::size_of_val` return the bytes which array occupies // A char takes 4 byte in Rust: Unicode char assert!(std::mem::size_of_val(&arr) == __); println!("Success!") }
- 🌟 All elements in an array can be initialized to the same value at once.
fn main() { // fill the blank let list: [i32; 100] = __ ; assert!(list[0] == 1); assert!(list.len() == 100); println!("Success!") }
- 🌟 All elements in an array must be of the same type
fn main() { // fix the error let _arr = [1, 2, '3']; println!("Success!") }
- 🌟 Indexing starts at 0.
fn main() { let arr = ['a', 'b', 'c']; let ele = arr[1]; // only modify this line to make the code work! assert!(ele == 'a'); println!("Success!") }
- 🌟 Out of bounds indexing causes
panic
.
// fix the error fn main() { let names = [String::from("Sunfei"), "Sunface".to_string()]; // `get` returns an Option<T>, it's safe to use let name0 = names.get(0).unwrap(); // but indexing is not safe let _name1 = &names[2]; println!("Success!") }
You can find the solutions here(under the solutions path), but only use it when you need it