Rust Platform

Shared references (&T) are read-only. To modify borrowed data, you need a mutable reference (&mut T):

fn add_greeting(text: &mut String) { text.push_str(", hello!"); } let mut message = String::from("World"); add_greeting(&mut message); assert_eq!(message, "World, hello!");

Python comparison

In Python, you can modify objects passed to functions because everything is a reference:

def add_item(items, item): items.append(item) my_list = [1, 2] add_item(my_list, 3) print(my_list) # [1, 2, 3]

This is convenient but dangerous — …