5. 列表、元组与模式解构

fn describe(xs: List[Int]) -> String =
  match xs {
    [] -> "空"
    [x] -> "单个 ${x}"
    [first, ..rest] -> "首个 ${first}，还有 ${len(rest)} 个"
  }

pub fn main() -> Unit !io = {
  println(describe([]))
  println(describe([9]))
  println(describe([1, 2, 3]))
}

空
单个 9
首个 1，还有 2 个

fn divmod(a: Int, b: Int) -> (Int, Int) = (a / b, a % b)

pub fn main() -> Unit !io = {
  let (q, r) = divmod(17, 5)
  println("${q} 余 ${r}")
}

3 余 2