rust 切片

fn main() {
  // 切片
  let s = String::from("Hello world");
  let substr = &s[1..6];
  let hello = &s[..5];
  let world = &s[6..];
  let whole = &s[..];
  println!("subtr： {}", substr);
  println!("hello： {}", hello);
  println!("world： {}", world);
  println!("whole： {}", whole);
}