| # Common Collections |
| |
| Rust’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 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 Rust 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 documentation][collections]. |
| |
| We’ll discuss how to create and update vectors, strings, and hash maps, as well |
| as what makes each special. |
| |
| [collections]: ../std/collections/index.html |
