Primitive and reference types

Primitives are values stored immediately on the stack. In Rust terminology, these types are Copy, so reassigning them to different values will create distinct copies of the underlying value.

The primitives available in Rune are:

  • The unit ().
  • Booleans, true and false.
  • Bytes, like b'\xff'.
  • Characters, like '今'. Which are 4 byte wide characters.
  • Integers, like 42. Which are 64-bit signed integers.
  • Floats, like 3.1418. Which are 64-bit floating point numbers.
  • Static strings, like "Hello World".
  • Type hashes.

You can see that these bytes are Copy when assigning them to a different variable, because a separate copy of the value will be used automatically.

let a = 1;
let b = a;
a = 2;
println!("{a}");
println!("{b}");

$> cargo run -- run scripts/book/primitives/copy.rn
2
1

Other types like strings are stored by reference. Assigning them to a different variable will only copy their reference, but they still point to the same underlying data.

let a = String::from("Hello");
let b = a;
a.push_str(" World");
println!("{a}");
println!("{b}");

$> cargo run -- run scripts/book/primitives/primitives.rn
Hello World
Hello World