Rust Platform

🎯 In Python, you never worry about integer size — math.factorial(100) returns a 158-digit number without breaking a sweat. Python integers grow as large as memory allows.

Rust integers have fixed sizes. A u64 maxes out at 18,446,744,073,709,551,615. That sounds huge, but 21! already exceeds it — factorials grow fast. In debug mode, Rust panics on integer overflow rather than silently wrapping around. This is a safety feature: it catches bugs that would go unnoticed in C.

The function signature uses u64 — enough to handle up to factorial(20).

Or-patterns in match

In the previous exercise you used match with individual arms. You can also combine multiple patterns with | (or):

match day {
    0 | 6 => println!("weekend"),  // matches 0 OR 6
    _ => println!("weekday"),
}

This is cleaner than writing two separate arms with the same body. Python's equivalent is case 0 | 6:.

Ranges — Rust's range()

If you go the iterative route, you'll want Rust's range syntax:

for i in 1..5 {
    print!("{i} ");  // 1 2 3 4 (exclusive end, like Python's range)
}

for i in 1..=5 {
    print!("{i} ");  // 1 2 3 4 5 (inclusive end)
}

1..5 is like Python's range(1, 5). 1..=5 includes the end — there's no direct Python equivalent, you'd write range(1, 6).

Ranges are iterators, so all the iterator methods work on them — .map(), .filter(), .fold(), and more.