This recipe is going to be a bit longer than the others, because:

• The vector is the most important collection
• Many of its core principles, like preallocation, apply to other collections as well
• It includes methods used on slices, which are also usable by many other collections

Let's start at the beginning.

A vector can be created [9] by using the constructor pattern we mentioned earlier (Chapter 1, Learning the Basics, Using the Constructor Pattern), and filled by calling push on it for every element we want to store [10]. Because this is such a common pattern, Rust provides you with a convenient macro called vec![3]. While its end effect is the same, the macro is implemented with some nice performance optimizations.

If you want to initialize a vector by repeating an element over and over...