[Rust] Option
fn multiply(num: Option<usize>) -> usize {
return num.unwrap_or(0) * 5;
}
fn multiply1(num: Option<usize>) -> Option<usize> {
match num {
Some(num) => Some(num * 5),
None => None,
}
}
fn multiply2(num: Option<usize>) -> Option<usize> {
return num.map(|x| x * 5);
}
fn multiply3(num: Option<usize>) -> Option<usize> {
return Some(num? * 5);
}