Skip to content

Use internal iteration in Iterator::is_sorted_by #82198

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Feb 17, 2021
Merged

Use internal iteration in Iterator::is_sorted_by #82198

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
25 changes: 16 additions & 9 deletions library/core/src/iter/traits/iterator.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3317,24 +3317,31 @@ pub trait Iterator {
///
/// [`is_sorted`]: Iterator::is_sorted
#[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
fn is_sorted_by<F>(mut self, mut compare: F) -> bool
fn is_sorted_by<F>(mut self, compare: F) -> bool
where
Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
{
#[inline]
fn check<'a, T>(
last: &'a mut T,
mut compare: impl FnMut(&T, &T) -> Option<Ordering> + 'a,
) -> impl FnMut(T) -> bool + 'a {
move |curr| {
if let Some(Ordering::Greater) | None = compare(&last, &curr) {
return false;
}
*last = curr;
true
}
}

let mut last = match self.next() {
Some(e) => e,
None => return true,
};

while let Some(curr) = self.next() {
if let Some(Ordering::Greater) | None = compare(&last, &curr) {
return false;
}
last = curr;
}

true
self.all(check(&mut last, compare))
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Seems like it'd be cleaner to just use a closure.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

All the other Iterator's methods use separate functions like that, I guess to reduce generics bloat.

Copy link
Member

@sfackler sfackler Feb 16, 2021 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Oh right, it avoids an extra implicit parameter of the actual iterator type I guess?

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is a really good use case for #77960.

}

/// Checks if the elements of this iterator are sorted using the given key extraction
Expand Down