Day 6: References & Borrowing

References allow you to refer to a value without taking ownership - this is called borrowing.

Two Types of References

Type	Syntax	Can Modify?	How Many?
Immutable	`&T`	No	Unlimited
Mutable	`&mut T`	Yes	Only one

Immutable References

fn calculate_length(s: &String) -> usize {
    s.len()
}  // s goes out of scope, but doesn't drop the String

let s = String::from("hello");
let len = calculate_length(&s);  // s is still valid!

Mutable References

fn add_world(s: &mut String) {
    s.push_str(" world");
}

let mut s = String::from("hello");
add_world(&mut s);  // s is now "hello world"

You can have either ONE mutable reference OR any number of immutable references - never both at once!

The Task

Implement two functions:

add_suffix - takes &mut String and appends "_modified"
get_length - takes &String and returns the length

Requirements

add_suffix should modify the string in place
get_length should not take ownership
Final output: rust_modified 13

Hints

Use s.push_str("_modified") to append
Use s.len() to get length
Remember: &mut for mutable, & for immutable