Rust

Feature	Immutable Variable (let)	Constants (const)
Evaluation	Runtime	Compile-time
Type	Optional (inferred)	Required
Scope	Block-local	Global or local
Use Case	Runtime values, immutable after assigned	Fixed values, known at compile time

Shadowing effectively creates a new variable with the same name as an existing one, allowing the reuse of the variable name while potentially altering its type or value.

let spaces = "    ";
let spaces = spaces.len();

Ownership

Each value in Rust has one and only one owner at a time.

drop: RAII

Variable bindings:

• Move semantics: default
• Copy semantics: bit-wise copy

The following actions can possibly transfer (move) ownership:

• Assignment
• Passing a variable to a function
• Returning values

Enum

enum Option<T> {
    None,
    Some(T,
}