// References: ref, box fn main() { // MUT REFS let mut p = 55; // take a mut ref let e: &mut i32 = &mut p; println!("e:&mut i32 is {}", e); // deref a mut ref *e = 65; println!("*e is {}", e); // WEAKENING THE TYPE // Weaken the ref by loosing mutability: &mut >> & // Original var is dropped, new eponymous var shadows it. // Type annotation is necessary for this coercion: let e: &i32 = e; println!("e:&i32 is {}", e); // since it is now just a ref, we can take another shared ref by copying it let w = e; // both refs are live println!("w:&i32 is {}; e:&i32 is {}", w, e); // BOX let b = Box::new(11_u8); println!("b:Box<u8> is {:?}", b); // Borrow use std::borrow::Borrow; // borrow() -- get a ref (from the box) to the boxed value -- get unboxed ref let f: &u8 = b.borrow(); assert_eq!(f, &11); // as_ref() -- get a ref (from the box) to the boxed value -- get unboxed ref let f: &u8 = b.as_ref(); assert_eq!(f, &11); // deref() -- get a ref (from the box) to the boxed value -- get unboxed ref use std::ops::Deref; let f: &u8 = b.deref(); assert_eq!(f, &11); // all such refs (from borrow, as_ref, deref) can be dereferenced: assert_eq!(*f, 11); // Box is apecial ref -- it can be derefed (unboxed) directly println!("b:u8 is {}", *b); } // main