Common Collections

Oxide's standard library includes a number of very useful data structures called collections. Most other data types represent one specific value, but collections can contain multiple values. Unlike the built-in array and tuple types, the data that these collections point to is stored on the heap, which means the amount of data does not need to be known at compile time and can grow or shrink as the program runs. Each kind of collection has different capabilities and costs, and choosing an appropriate one for your current situation is a skill you'll develop over time. In this chapter, we'll discuss three collections that are used very often in Oxide programs:

• A vector allows you to store a variable number of values next to each other.
• A string is a collection of characters. We've mentioned the String type previously, but in this chapter we'll talk about it in depth.
• A hash map allows you to associate a value with a specific key. It's a particular implementation of the more general data structure called a map.

To learn about the other kinds of collections provided by the standard library, see the standard library documentation.

We'll discuss how to create and update vectors, strings, and hash maps, as well as what makes each special.

Collection Types in Oxide

Oxide uses Rust's standard collection types directly. There are no type aliases for collections in Oxide v1.0:

This design keeps things simple and ensures you learn Rust's actual collection types, which is essential for reading documentation and understanding how your code works under the hood.

Rust comparison: The collection types are identical to Rust. Oxide uses the same Vec<T>, String, and HashMap<K, V> types.

#![allow(unused)]
fn main() {
// Rust - identical syntax
use std::collections::HashMap;
let v: Vec<i32> = Vec::new();
let s: String = String::new();
let h: HashMap<String, i32> = HashMap::new();
}