What Are (Rust) Macros

(not azriel's) Definition: Copy-paste code without the pasta. And varargs.

• Shortcode:

  Original:

  
  #![allow(unused_variables)]
  fn main() {
  use std::ops::Add;
  
  #[derive(Clone, Copy, PartialEq)]
  pub struct HealthPoints(pub u32);
  
  impl Add for HealthPoints {
      type Output = HealthPoints;
  
      fn add(self, other: HealthPoints) -> HealthPoints {
          HealthPoints(self.0 + other.0)
      }
  }
  }
  

  Macro-treated:

  #[derive(derive_more::Add, Clone, Copy, PartialEq)]
  pub struct HealthPoints(pub u32);
  

• Varargs:

  
  #![allow(unused_variables)]
  fn main() {
  let (a, b) = (3., 2.);
  
  println!();
  println!("hello");
  println!(
      "{a:.1} ÷ {b:.1} = {answer:.2}",
      a = a,
      b = b,
      answer = a / b
  );
  }