Rust函数

函数使用fn关键字声明。 其参数的数据类型注解,就像变量,并且如果该函数返回一个值,返回类型必须箭头后指定 ->.

在函数的最终表达式将被用作返回值。或者, return语句可用于早期从函数内返回一个值,即使从内循环或 if 语句

让我们改写FizzBuzz使用函数!

// Unlike C/C++, there's no restriction on the order of function definitions
fn main() {
    // We can use this function here, and define it somewhere later
    fizzbuzz_to(100);
}

// Function that returns a boolean value
fn is_divisible_by(lhs: u32, rhs: u32) -> bool {
    // Corner case, early return
    if rhs == 0 {
        return false;
    }

    // This is an expression, the `return` keyword is not necessary here
    lhs % rhs == 0
}

// Functions that "don't" return a value, actually return the unit type `()`
fn fizzbuzz(n: u32) -> () {
    if is_divisible_by(n, 15) {
        println!("fizzbuzz");
    } else if is_divisible_by(n, 3) {
        println!("fizz");
    } else if is_divisible_by(n, 5) {
        println!("buzz");
    } else {
        println!("{}", n);
    }
}

// When a function returns `()`, the return type can be omitted from the
// signature
fn fizzbuzz_to(n: u32) {
    for n in 1..n + 1 {
        fizzbuzz(n);
    }
}

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