Main exercises

This commit is contained in:
Nidhal Messaoudi 2023-02-27 21:36:51 +01:00
parent 278a1f103b
commit 34aafa82f9
6 changed files with 52 additions and 23 deletions

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@ -4,7 +4,7 @@
// This exercise uses some concepts that we won't get to until later in the course, like `Box` and the
// `From` trait. It's not important to understand them in detail right now, but you can read ahead if you like.
// For now, think of the `Box<dyn ...>` type as an "I want anything that does ???" type, which, given
// For now, think of the `Box<dyn ???>` type as an "I want anything that does ???" type, which, given
// Rust's usual standards for runtime safety, should strike you as somewhat lenient!
// In short, this particular use case for boxes is for when you want to own a value and you care only that it is a

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@ -3,6 +3,7 @@
// I AM NOT DONE
#[rustfmt::skip]
macro_rules! my_macro {
() => {
println!("Check out my macro!");

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@ -32,7 +32,7 @@ fn main() {
for offset in 0..8 {
let child_numbers = // TODO
joinhandles.push(thread::spawn(move || {
let sum: u32 = child_numbers.iter().filter(|n| *n % 8 == offset).sum();
let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();
println!("Sum of offset {} is {}", offset, sum);
}));
}

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@ -4,6 +4,9 @@
// Cow is a clone-on-write smart pointer.
// It can enclose and provide immutable access to borrowed data, and clone the data lazily when mutation or ownership is required.
// The type is designed to work with general borrowed data via the Borrow trait.
//
// This exercise is meant to show you what to expect when passing data to Cow.
// Fix the unit tests by checking for Cow::Owned(_) and Cow::Borrowed(_) at the TODO markers.
// I AM NOT DONE
@ -20,29 +23,52 @@ fn abs_all<'a, 'b>(input: &'a mut Cow<'b, [i32]>) -> &'a mut Cow<'b, [i32]> {
input
}
fn main() {
// No clone occurs because `input` doesn't need to be mutated.
let slice = [0, 1, 2];
let mut input = Cow::from(&slice[..]);
match abs_all(&mut input) {
Cow::Borrowed(_) => println!("I borrowed the slice!"),
_ => panic!("expected borrowed value"),
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn reference_mutation() -> Result<(), &'static str> {
// Clone occurs because `input` needs to be mutated.
let slice = [-1, 0, 1];
let mut input = Cow::from(&slice[..]);
match abs_all(&mut input) {
Cow::Owned(_) => println!("I modified the slice and now own it!"),
_ => panic!("expected owned value"),
Cow::Owned(_) => Ok(()),
_ => Err("Expected owned value"),
}
}
// No clone occurs because `input` is already owned.
#[test]
fn reference_no_mutation() -> Result<(), &'static str> {
// No clone occurs because `input` doesn't need to be mutated.
let slice = [0, 1, 2];
let mut input = Cow::from(&slice[..]);
match abs_all(&mut input) {
// TODO
}
}
#[test]
fn owned_no_mutation() -> Result<(), &'static str> {
// We can also pass `slice` without `&` so Cow owns it directly.
// In this case no mutation occurs and thus also no clone,
// but the result is still owned because it always was.
let slice = vec![0, 1, 2];
let mut input = Cow::from(slice);
match abs_all(&mut input) {
// TODO
}
}
#[test]
fn owned_mutation() -> Result<(), &'static str> {
// Of course this is also the case if a mutation does occur.
// In this case the call to `to_mut()` returns a reference to
// the same data as before.
let slice = vec![-1, 0, 1];
let mut input = Cow::from(slice);
match abs_all(&mut input) {
// TODO
Cow::Borrowed(_) => println!("I own this slice!"),
_ => panic!("expected borrowed value"),
}
}
}

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@ -13,3 +13,5 @@ the other useful data structure, hash maps, later.
## Further information
- [Storing Lists of Values with Vectors](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)
- [`iter_mut`](https://doc.rust-lang.org/std/primitive.slice.html#method.iter_mut)
- [`map`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.map)