feat: Add box1.rs exercise
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For the Box exercise check out the chapter [Using Box to Point to Data on the Heap](https://doc.rust-lang.org/book/ch15-01-box.html).
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For the Arc exercise check out the chapter [Shared-State Concurrency](https://doc.rust-lang.org/book/ch16-03-shared-state.html) of the Rust Book.
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For the Arc exercise check out the chapter [Shared-State Concurrency](https://doc.rust-lang.org/book/ch16-03-shared-state.html) of the Rust Book.
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For the Iterator exercise check out the chapters [Iterator](https://doc.rust-lang.org/book/ch13-02-iterators.html) of the Rust Book and the [Iterator documentation](https://doc.rust-lang.org/stable/std/iter/).
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For the Iterator exercise check out the chapters [Iterator](https://doc.rust-lang.org/book/ch13-02-iterators.html) of the Rust Book and the [Iterator documentation](https://doc.rust-lang.org/stable/std/iter/).
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// box1.rs
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//
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// At compile time, Rust needs to know how much space a type takes up. This becomes problematic
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// for recursive types, where a value can have as part of itself another value of the same type.
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// To get around the issue, we can use a `Box` - a smart pointer used to store data on the heap,
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// which also allows us to wrap a recursive type.
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//
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// The recursive type we're implementing in this exercise is the `cons list` - a data structure
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// frequently found in functional programming languages. Each item in a cons list contains two
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// elements: the value of the current item and the next item. The last item is a value called `Nil`.
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//
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// Step 1: use a `Box` in the enum definition to make the code compile
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// Step 2: create both empty and non-empty cons lists of by replacing `unimplemented!()`
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//
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// Execute `rustlings hint box1` for hints :)
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// I AM NOT DONE
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#[derive(PartialEq, Debug)]
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enum List {
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Cons(i32, List),
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Nil,
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}
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fn main() {
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let empty_list = unimplemented!();
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println!("This is an empty cons list: {:?}", empty_list);
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let non_empty_list = unimplemented!();
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println!("This is a non-empty cons list: {:?}", non_empty_list);
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// Do not change these
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assert_eq!(List::Nil, empty_list);
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assert_ne!(empty_list, non_empty_list);
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}
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18
info.toml
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info.toml
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@ -614,6 +614,24 @@ hint = """
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# STANDARD LIBRARY TYPES
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# STANDARD LIBRARY TYPES
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[[exercises]]
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name = "box1"
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path = "exercises/standard_library_types/box1.rs"
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mode = "compile"
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hint = """
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Step 1
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The compiler's message should help: since we cannot store the value of the actual type
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when working with recursive types, we need to store a reference (pointer) to its value.
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We should therefore place our `List` inside a `Box`. More details in the book here:
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https://doc.rust-lang.org/book/ch15-01-box.html#enabling-recursive-types-with-boxes
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Step 2
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Creating an empty list should be fairly straightforward (hint: peek at the assertions).
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For a non-empty list keep in mind that wee want to use our Cons "list builder".
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Although the current list is one of integers (i32), feel free to change the definition
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and try other types!
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"""
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[[exercises]]
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[[exercises]]
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name = "arc1"
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name = "arc1"
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path = "exercises/standard_library_types/arc1.rs"
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path = "exercises/standard_library_types/arc1.rs"
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