Variables are immutable by default in Rust, but they're not const by default. The difference is that a variable can become mutable while a const is always immutable.

How do you set a variable as mutable after the fact in rust?

You can do:

    let foo = "1234".to_string();
    let mut foo = foo;
    foo = "5678";

This only works if you have ownership of the variable though. And in practice it's a pretty good compromise, because it's pretty hard to do this by mistake.

Note: const in rust is different to const in some other languages: it represents a value that is duplicated inline into each use site at compile time.

Yes I think i see it more like constexpr.