= Rust Mutability =

A description of '''mutability''' (and '''immutability''') in Rust.

<<TableOfContents>>

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== Description ==

Most variables are actually immutable by default.

To ''enable'' mutability, a variable must be declared with the `mut` keyword.

{{{
fn main() {
    let mut x = 0;
    x = 1;
}
}}}

It ''is'' possible to '''shadow''' a variable name, however.

{{{
fn main() {
    let spaces = "   ";
    let spaces = spaces.len();
}
}}}

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== Tips ==

=== Global Scope ===

Rust does not allow variables in the global scope. To place a value there, try:

 1. declare a string literal (i.e. `const THRESHOLD: i32 = 10`)
 2. use a function that returns a value given the `'static` reference lifetime

{{{
fn coerce_static<'a>(_: &'a i32) -> &'a i32 {
    &NUM
}

fn main() {
    let lifetime_num = 9;
    let coerced_static = coerce_static(&lifetime_num);
}
}}}



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CategoryRicottone