Merge pull request #409 from AlexandruGG/feature/box-exercise

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fmoko 2020-05-30 17:58:16 +02:00 committed by GitHub
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.gitignore vendored
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@ -5,3 +5,4 @@ target/
*.pdb *.pdb
exercises/clippy/Cargo.toml exercises/clippy/Cargo.toml
exercises/clippy/Cargo.lock exercises/clippy/Cargo.lock
.idea

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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).
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 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/). 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
//
// 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())
}
}

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@ -614,6 +614,24 @@ hint = """
# STANDARD LIBRARY TYPES # 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]] [[exercises]]
name = "arc1" name = "arc1"
path = "exercises/standard_library_types/arc1.rs" path = "exercises/standard_library_types/arc1.rs"