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Implements PartialEq and Eq for Deque #521

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1 change: 1 addition & 0 deletions CHANGELOG.md
Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
- Added `SortedLinkedListView`, the `!Sized` version of `SortedLinkedList`.
- Added implementation of `Borrow` and `BorrowMut` for `String` and `Vec`.
- Added `Deque::{swap, swap_unchecked, swap_remove_front, swap_remove_back}`.
- Implemented `PartialEq` and `Eq` for `Deque`.

### Changed

Expand Down
99 changes: 99 additions & 0 deletions src/deque.rs
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
//! ```

use core::borrow::{Borrow, BorrowMut};
use core::cmp::Ordering;
use core::fmt;
use core::iter::FusedIterator;
use core::mem::MaybeUninit;
Expand Down Expand Up @@ -950,6 +951,48 @@ where
}
}

impl<T: PartialEq, const N: usize> PartialEq for Deque<T, N> {
fn eq(&self, other: &Self) -> bool {
if self.len() != other.len() {
return false;
}
let (sa, sb) = self.as_slices();
let (oa, ob) = other.as_slices();
match sa.len().cmp(&oa.len()) {
Ordering::Equal => sa == oa && sb == ob,
Ordering::Less => {
// Always divisible in three sections, for example:
// self: [a b c|d e f]
// other: [0 1 2 3|4 5]
// front = 3, mid = 1,
// [a b c] == [0 1 2] && [d] == [3] && [e f] == [4 5]
let front = sa.len();
let mid = oa.len() - front;

let (oa_front, oa_mid) = oa.split_at(front);
let (sb_mid, sb_back) = sb.split_at(mid);
debug_assert_eq!(sa.len(), oa_front.len());
debug_assert_eq!(sb_mid.len(), oa_mid.len());
debug_assert_eq!(sb_back.len(), ob.len());
sa == oa_front && sb_mid == oa_mid && sb_back == ob
}
Ordering::Greater => {
let front = oa.len();
let mid = sa.len() - front;

let (sa_front, sa_mid) = sa.split_at(front);
let (ob_mid, ob_back) = ob.split_at(mid);
debug_assert_eq!(sa_front.len(), oa.len());
debug_assert_eq!(sa_mid.len(), ob_mid.len());
debug_assert_eq!(sb.len(), ob_back.len());
sa_front == oa && sa_mid == ob_mid && sb == ob_back
}
}
}
}

impl<T: Eq, const N: usize> Eq for Deque<T, N> {}

#[cfg(test)]
mod tests {
use static_assertions::assert_not_impl_any;
Expand Down Expand Up @@ -1440,4 +1483,60 @@ mod tests {
q.pop_front().unwrap();
q.swap(0, 2);
}

#[test]
fn equality() {
let mut a: Deque<i32, 7> = Deque::new();
let mut b: Deque<i32, 7> = Deque::new();

assert_eq!(a, b);

a.push_back(1).unwrap();
a.push_back(2).unwrap();
a.push_back(3).unwrap();

assert_ne!(a, b);

b.push_back(1).unwrap();
b.push_back(2).unwrap();
b.push_back(3).unwrap();

assert_eq!(a, b);

a.push_back(1).unwrap();
a.push_back(2).unwrap();
a.push_back(3).unwrap();

assert_ne!(a, b);

b.push_front(3).unwrap();
b.push_front(2).unwrap();
b.push_front(1).unwrap();

assert_eq!(a, b);

a.push_back(4).unwrap();
b.push_back(4).unwrap();

assert_eq!(a, b);

a.clear();
b.clear();

a.push_back(1).unwrap();
a.push_back(2).unwrap();
a.push_back(3).unwrap();
a.push_front(3).unwrap();
a.push_front(2).unwrap();
a.push_front(1).unwrap();

b.push_back(2).unwrap();
b.push_back(3).unwrap();
b.push_back(1).unwrap();
b.push_back(2).unwrap();
b.push_back(3).unwrap();
b.push_front(1).unwrap();

assert_eq!(a, b);
}
}
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