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| -rw-r--r-- | .gitignore | 1 | ||||
| -rw-r--r-- | exercises/standard_library_types/README.md | 2 | ||||
| -rw-r--r-- | exercises/standard_library_types/box1.rs | 53 | ||||
| -rw-r--r-- | info.toml | 18 |
4 files changed, 74 insertions, 0 deletions
@@ -5,3 +5,4 @@ target/ *.pdb exercises/clippy/Cargo.toml exercises/clippy/Cargo.lock +.idea diff --git a/exercises/standard_library_types/README.md b/exercises/standard_library_types/README.md index d138d87..36b30c1 100644 --- a/exercises/standard_library_types/README.md +++ b/exercises/standard_library_types/README.md @@ -1,3 +1,5 @@ +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). + 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. 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/). diff --git a/exercises/standard_library_types/box1.rs b/exercises/standard_library_types/box1.rs new file mode 100644 index 0000000..2248962 --- /dev/null +++ b/exercises/standard_library_types/box1.rs @@ -0,0 +1,53 @@ +// box1.rs +// +// 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. +// +// 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`. +// +// Step 1: use a `Box` in the enum definition to make the code compile +// Step 2: create both empty and non-empty cons lists of by replacing `unimplemented!()` +// +// Note: the tests should not be changed +// +// Execute `rustlings hint box1` for hints :) + +// I AM NOT DONE + +#[derive(PartialEq, Debug)] +pub enum List { + Cons(i32, List), + Nil, +} + +fn main() { + println!("This is an empty cons list: {:?}", create_empty_list()); + println!("This is a non-empty cons list: {:?}", create_non_empty_list()); +} + +pub fn create_empty_list() -> List { + unimplemented!() +} + +pub fn create_non_empty_list() -> List { + unimplemented!() +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn test_create_empty_list() { + assert_eq!(List::Nil, create_empty_list()) + } + + #[test] + fn test_create_non_empty_list() { + assert_ne!(create_empty_list(), create_non_empty_list()) + } +} @@ -615,6 +615,24 @@ hint = """ # STANDARD LIBRARY TYPES [[exercises]] +name = "box1" +path = "exercises/standard_library_types/box1.rs" +mode = "test" +hint = """ +Step 1 +The compiler's message should help: since we cannot store the value of the actual type +when working with recursive types, we need to store a reference (pointer) to its value. +We should, therefore, place our `List` inside a `Box`. More details in the book here: +https://doc.rust-lang.org/book/ch15-01-box.html#enabling-recursive-types-with-boxes + +Step 2 +Creating an empty list should be fairly straightforward (hint: peek at the assertions). +For a non-empty list keep in mind that we want to use our Cons "list builder". +Although the current list is one of integers (i32), feel free to change the definition +and try other types! +""" + +[[exercises]] name = "arc1" path = "exercises/standard_library_types/arc1.rs" mode = "compile" |