rust map

fn test_map(){
    let a=[1,2,3];
    let mut iter = a.into_iter().map(|x|2*x);
    let b = a.into_iter().map(|x|3*x).collect::<Vec<i32>>();
    println!("a:{:?}",iter.next());
    println!("b:{:?}",b);
    let arr = ["1","b","3"];
    let c = arr.iter().filter_map(|x|x.parse().ok()).collect::<Vec<i32>>();
    println!("c:{:?}",c);
    let mut rever = arr.iter().rev();
    println!("reverse:{:?}",rever.next());
}

a:Some(2)
b:[3, 6, 9]
c:[1, 3]
reverse:Some("3")