Rust Brain Teasers: description (Puzzle15: To Infinity)
On this line:
fn fmt(&self, f: &mut fmt::Formatter<`_>) -> fmt::Result {
Formatter<`_> is flagged as an error (“this struct takes 0 generic arguments but 1 generic argument was supplied”).
When I “correct” it to f: &mut fmt::Formatter then the program runs just fine) only spits out one line and exits normally. It does not spit out node after node until it gets a stack overflow.
I do get a “dead code” warning on the prev property of Node, so maybe that’s being optimized out, thus avoiding your error?
Full source for reference:
use std::cell::RefCell;
use std::rc::Rc;
type Link = Option<Rc<RefCell<Node>>>;
// #[derive(Debug)]
struct Node {
elem: i32,
next: Link,
prev: Link,
}
impl Node {}
use std::fmt;
impl fmt::Debug for Node {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "elem: {}", self.elem)
}
}
fn main() {
let mut head = Some(Rc::new(RefCell::new(Node {
elem: 1,
next: None,
prev: None,
})));
head.as_mut().unwrap().borrow_mut().next = Some(Rc::new(RefCell::new(Node {
elem: 2,
next: None,
prev: head.clone(),
})));
println!("{:?}", head);
}
also for reference:
rustup show
Default host: x86_64-apple-darwin
rustup home: /Users/mike/.rustup
installed toolchains
--------------------
stable-x86_64-apple-darwin (default)
nightly-x86_64-apple-darwin
installed targets for active toolchain
--------------------------------------
wasm32-unknown-unknown
x86_64-apple-darwin
active toolchain
----------------
stable-x86_64-apple-darwin (default)
rustc 1.55.0 (c8dfcfe04 2021-09-06)