Functions

A Rust version of the famous FizzBuzz interview question:

fn main() {
    print_fizzbuzz_to(20);
}

fn is_divisible(n: u32, divisor: u32) -> bool {
    if divisor == 0 {
        return false;
    }
    n % divisor == 0
}

fn fizzbuzz(n: u32) -> String {
    let fizz = if is_divisible(n, 3) { "fizz" } else { "" };
    let buzz = if is_divisible(n, 5) { "buzz" } else { "" };
    if fizz.is_empty() && buzz.is_empty() {
        return format!("{n}");
    }
    format!("{fizz}{buzz}")
}

fn print_fizzbuzz_to(n: u32) {
    for i in 1..=n {
        println!("{}", fizzbuzz(i));
    }
}
  • We refer in main to a function written below. Neither forward declarations nor headers are necessary.
  • Declaration parameters are followed by a type (the reverse of some programming languages), then a return type.
  • The last expression in a function body (or any block) becomes the return value. Simply omit the ; at the end of the expression.
  • Some functions have no return value, and return the ‘unit type’, (). The compiler will infer this if the -> () return type is omitted.
  • The range expression in the for loop in print_fizzbuzz_to() contains =n, which causes it to include the upper bound.