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// 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
Rust
INFO