2023-05-29 20:39:08 +03:00
|
|
|
// At compile time, Rust needs to know how much space a type takes up. This
|
|
|
|
// becomes problematic for recursive types, where a value can have as part of
|
|
|
|
// itself another value of the same type. To get around the issue, we can use a
|
|
|
|
// `Box` - a smart pointer used to store data on the heap, which also allows us
|
|
|
|
// to wrap a recursive type.
|
2020-05-26 23:46:24 +03:00
|
|
|
//
|
2023-05-29 20:39:08 +03:00
|
|
|
// The recursive type we're implementing in this exercise is the `cons list` - a
|
|
|
|
// data structure frequently found in functional programming languages. Each
|
|
|
|
// item in a cons list contains two elements: the value of the current item and
|
|
|
|
// the next item. The last item is a value called `Nil`.
|
2020-05-26 23:46:24 +03:00
|
|
|
//
|
|
|
|
// Step 1: use a `Box` in the enum definition to make the code compile
|
2022-07-30 17:50:07 +03:00
|
|
|
// Step 2: create both empty and non-empty cons lists by replacing `todo!()`
|
2020-05-26 23:46:24 +03:00
|
|
|
//
|
2020-05-27 12:03:59 +03:00
|
|
|
// Note: the tests should not be changed
|
2020-05-26 23:46:24 +03:00
|
|
|
|
|
|
|
#[derive(PartialEq, Debug)]
|
2024-05-22 16:04:12 +03:00
|
|
|
enum List {
|
2020-05-26 23:46:24 +03:00
|
|
|
Cons(i32, List),
|
|
|
|
Nil,
|
|
|
|
}
|
|
|
|
|
|
|
|
fn main() {
|
2020-05-27 12:03:59 +03:00
|
|
|
println!("This is an empty cons list: {:?}", create_empty_list());
|
2020-08-10 17:24:21 +03:00
|
|
|
println!(
|
|
|
|
"This is a non-empty cons list: {:?}",
|
|
|
|
create_non_empty_list()
|
|
|
|
);
|
2020-05-27 12:03:59 +03:00
|
|
|
}
|
|
|
|
|
2024-05-22 16:04:12 +03:00
|
|
|
fn create_empty_list() -> List {
|
2022-07-30 17:50:07 +03:00
|
|
|
todo!()
|
2020-05-27 12:03:59 +03:00
|
|
|
}
|
|
|
|
|
2024-05-22 16:04:12 +03:00
|
|
|
fn create_non_empty_list() -> List {
|
2022-07-30 17:50:07 +03:00
|
|
|
todo!()
|
2020-05-27 12:03:59 +03:00
|
|
|
}
|
|
|
|
|
|
|
|
#[cfg(test)]
|
|
|
|
mod tests {
|
|
|
|
use super::*;
|
2020-05-26 23:46:24 +03:00
|
|
|
|
2020-05-27 12:03:59 +03:00
|
|
|
#[test]
|
|
|
|
fn test_create_empty_list() {
|
2024-05-22 16:13:18 +03:00
|
|
|
assert_eq!(List::Nil, create_empty_list());
|
2020-05-27 12:03:59 +03:00
|
|
|
}
|
2020-05-26 23:46:24 +03:00
|
|
|
|
2020-05-27 12:03:59 +03:00
|
|
|
#[test]
|
|
|
|
fn test_create_non_empty_list() {
|
2024-05-22 16:13:18 +03:00
|
|
|
assert_ne!(create_empty_list(), create_non_empty_list());
|
2020-05-27 12:03:59 +03:00
|
|
|
}
|
2020-05-26 23:46:24 +03:00
|
|
|
}
|