Rust Programming Cookbook

How to do it...

By following these next few steps, you will be able to use macros:

1. Run cargo new matching --lib in Terminal (or PowerShell on Windows) and open the directory with Visual Studio Code.
2. In src/lib.rs, we add a macro to work with specific types as inputs. Insert the following at the top of the file:

macro_rules! strange_patterns {    (The pattern must match precisely) => { "Text" };    (42) => { "Numeric" };    (;<=,<=;) => { "Alpha" };}

3. Clearly, this should be tested to see whether it works. Replace the it_works() test with a different test function:

    #[test]    fn test_strange_patterns() {        assert_eq!(strange_patterns!(The pattern must match         precisely), "Text");        assert_eq!(strange_patterns!(42), "Numeric"); assert_eq!(strange_patterns!(;<=,<=;), ...