Creating lazy static objects

Big objects, especially constant ones, should be reused instead of rebuilt. The lazy_static! macro helps you with this by extending Rust's normal static functionality, which normally requires your objects to be constructable at compile-time, with the ability to create lazy objects that are initialized during runtime.

How to do it...

1. Create a Rust project to work on during this chapter with cargo new chapter_five.
2. Navigate into the newly created chapter_five folder. For the rest of this chapter, we will assume that your command line is currently in this directory.
3. Inside the src folder, create a new folder called bin.
4. Delete the generated lib.rs file, as we are not creating a library.

5. Open the Cargo.toml file that was generated earlier for you.

6. Under [dependencies], add the following lines:

lazy_static = "1.0"
regex = "0.2"

If you want, you can go to the crates.io web pages for lazy_static (https://crates.io/crates/lazy_static) and regex (https://crates.io/crates/regex...