Variables and Mutability

Variables in Rust

In Rust, variables are declared with let and are immutable by default — once bound to a value, they cannot be changed:

let x = 5;
// x = 6; // ERROR: cannot assign twice to immutable variable

To make a variable mutable, add mut:

let mut count = 0;
count += 1; // OK

Type Inference

Rust infers types from context — you don't always need to annotate them:

let x = 42;       // i32
let y = 3.14;     // f64
let name = "Rust"; // &str

But you can be explicit:

let x: i32 = 42;
let y: f64 = 3.14;

Shadowing

Rust lets you declare a new variable with the same name, shadowing the previous one. Shadowing is different from mutation — it creates a brand new variable:

let x = 5;
let x = x + 1;   // shadows the previous x
let x = x * 2;   // shadows again
println!("{}", x); // 12

Shadowing allows changing the type, which mut does not:

let spaces = "   ";      // &str
let spaces = spaces.len(); // usize — OK with shadowing

Constants

Constants are always immutable and must have a type annotation. They can be defined in any scope:

const MAX_POINTS: u32 = 100_000;

Your Task

Implement two functions:

1. shadowing(x: i32) -> i32 — shadows the parameter: first add 1, then multiply by 2, return the result.
2. celsius_to_fahrenheit(c: f64) -> f64 — converts Celsius to Fahrenheit using the formula c * 9.0 / 5.0 + 32.0.