函数
函数使用fn关键字声明。%uA0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%uA0->.
在函数的最终表达式将被用作返回值。或者，%uA0return语句可用于早期从函数内返回一个值，即使从内循环或%uA0if%uA0语句
让我们改写FizzBuzz使用函数！
%uA0
// Unlike C/C++, there&aposs 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&apost" 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)
}
}