fn main() {
   
    assert_eq!( 10_i8 as u16, 10_u16); // 范围内转换

    let s = 10_i64;
    println!("{}",s);

    println!("{}",(-4_i32).abs());


    let t = ("Brazil", 1985);

    println!("{}",t.0);


    let text = "I see the eigenvalue in thine eye";
    let (head, tail) = text.split_at(1);

    println!("{}",head);
}