feat: add rc1.rs exercise

This commit is contained in:
Denton24646 2022-07-16 15:31:37 -04:00
parent c791cf4232
commit ce86d252e5
2 changed files with 112 additions and 0 deletions

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// rc1.rs
// In this exercise, we want to express the concept of multiple owners via the Rc<T> type.
// This is a model of our solar system - there is a Sun type and multiple Planets.
// The Planets take ownership of the sun, indicating that they revolve around the sun.
// Make this code compile by using the proper Rc primitives to express that the sun has multiple owners.
// I AM NOT DONE
use std::rc::Rc;
#[derive(Debug)]
struct Sun {}
#[derive(Debug)]
enum Planet {
Mercury(Rc<Sun>),
Venus(Rc<Sun>),
Earth(Rc<Sun>),
Mars(Rc<Sun>),
Jupiter(Rc<Sun>),
Saturn(Rc<Sun>),
Uranus(Rc<Sun>),
Neptune(Rc<Sun>),
}
impl Planet {
fn details(&self) {
println!("Hi from {:?}!", self)
}
}
fn main() {
let sun = Rc::new(Sun {});
println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
let mercury = Planet::Mercury(Rc::clone(&sun));
println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
mercury.details();
let venus = Planet::Venus(Rc::clone(&sun));
println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
venus.details();
let earth = Planet::Earth(Rc::clone(&sun));
println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
earth.details();
let mars = Planet::Mars(Rc::clone(&sun));
println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
mars.details();
let jupiter = Planet::Jupiter(Rc::clone(&sun));
println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
jupiter.details();
// TODO
let saturn = Planet::Saturn(Rc::new(Sun {}));
println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
saturn.details();
// TODO
let uranus = Planet::Uranus(Rc::new(Sun {}));
println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
uranus.details();
// TODO
let neptune = Planet::Neptune(Rc::new(Sun {}));
println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
neptune.details();
assert_eq!(Rc::strong_count(&sun), 9);
drop(neptune);
println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
drop(uranus);
println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
drop(saturn);
println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
drop(jupiter);
println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
drop(mars);
println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
// TODO
println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
// TODO
println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
// TODO
println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
assert_eq!(Rc::strong_count(&sun), 1);
}

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@ -929,6 +929,20 @@ is too much of a struggle, consider reading through all of Chapter 16 in the boo
https://doc.rust-lang.org/stable/book/ch16-00-concurrency.html
"""
[[exercises]]
name = "rc1"
path = "exercises/standard_library_types/rc1.rs"
mode = "compile"
hint = """
This is a straightforward exercise to use the Rc<T> type. Each Planet has
ownership of the Sun, and uses Rc::clone() to increment the reference count of the Sun.
After using drop() to move the Planets out of scope individually, the reference count goes down.
In the end the sun only has one reference again, to itself. See more at:
https://doc.rust-lang.org/book/ch15-04-rc.html
* Unforunately Pluto is no longer considered a planet :(
"""
# THREADS
[[exercises]]