Rust Essentials - Second Edition

Printing with string interpolation

An obvious way to use variables is to print out their value, as is done here:

// see Chapter 2/code/constants2.rs 
static MAX_HEALTH: i32 = 100; 
static GAME_NAME: &str = "Monster Attack"; 
const MYPI: f32 = 3.14; 
 
fn main() { 
  println!("The Game you are playing is called {}.", GAME_NAME); 
  println!("You start with {} health points.", MAX_HEALTH); 
} 

This gives an output which looks like this:

The Game you are playing is called Monster Attack.
You start with 100 health points.

The first argument of the println! macro is a literal format string containing a placeholder {}. The value of the constant or variable after the comma is converted to a string and comes in its place. There can be more than one placeholder ...