I have some code (below) and the results when running are the same but I am printing num and also *num. Does anyone understand and can say why num and *num generates the same output?
fn main() {
let v = vec![1,2,2,4,4];
for num in &v {
println!("{}", *num);
}
for num in &v {
println!("{}", num);
}
println!("{:?}", v);
}
1
2
2
4
4
1
2
2
4
4
[1, 2, 2, 4, 4]
Welcome! Please see the pinned code formatting post.
Printing via {} is performed by the Display trait, and if a type T implements Display, then all levels of references &T, &&T, &&&&&&&&&T, etc, defer to that same implementation.
In the first loop, you're dereferencing an &i32 and printing the i32. In the second loop, you're just printing the &i32, but again, the output is going to be the same as with the i32.
(Depending on how the println! macro is implemented, you might even be printing &i32 and &&i32 technically.)
Here's the implementation that shows that all layers of &&&T defer to T: Display (though it may not be obvious until you have more practice reading implementation signatures such as this one).
If you are interested in printing the pointer, you can do so with the following
println!("{:p}", num);