Hands-On Data Structures and Algorithms with Rust

Macros

Another aspect of Rust is the ability to do metaprogramming—basically programming programming—using macros! Macros are expanded in Rust code before compilation, which gives them more power than a regular function. The generated code can, for instance, create functions on the fly or implement traits for a structure.

These pieces of code make everyday life a lot easier by reducing the need to create and then initialize vectors, deriving the ability to clone a structure, or simply printing stuff to the command line.

This is a simplified example for the declarative vec![] macro provided in the Rust Book (second edition, Appendix D):

#[macro_export] macro_rules! vec {     ( $( $x:expr ),* ) => {         {                         let mut temp_vec = Vec::new();               $( temp_vec.push($x); ...