Building custom macros in Rust

Previously, we have mostly used predefined macros—it's now time to look at creating custom macros. There are several types of macros in Rust—derive-based, function-like, and attributes, all of which have their own respective use cases. In this recipe, we'll experiment with the function-like variety to get started.

How to do it...

You are only a few steps from creating macros:

1. Run cargo new custom-macros in Terminal (or PowerShell on Windows) and open the directory with Visual Studio Code.
2. Open src/main.rs in the editor. Let's create a new macro called one_plus_one at the top of the file:

// A simple macro without arguments
macro_rules! one_plus_one {
    () =&gt...