Ownership_and_Borrow.rs

struct Foo {
    x: i32,
}

fn do_something(f: Foo) {
    println!("{}", f.x);
    // f is dropped here
}

fn main() {
    let mut foo = Foo { x: 42 };
    let f = &mut foo;

    // FAILURE: do_something(foo) would fail because
    // foo cannot be moved while mutably borrowed

    // FAILURE: foo.x = 13; would fail here because
    // foo is not modifiable while mutably borrowed

    f.x = 13;
    // f is dropped here because it's no longer used after this point
    
    println!("{}", foo.x);
    
    // this works now because all mutable references were dropped
    foo.x = 7;
    
    // move foo's ownership to a function
    do_something(foo);

    let mut a= 42; 
    let b = &mut a; 
    let r  = *b;
    *b= 7; 
    println!("a={}",a); 
    // println!("{}",b);
    println!("r={}",r); 





}