Correct iterator adaptor Chain #27991
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
(rust_highfive has picked a reviewer for you, use r? to override) |
|
r? @gankro |
bluss
force-pushed
the
chain-rev
branch
4 times, most recently
from
90e9de5 to
a5d6eaa
Compare
|
Could you add a comment to |
The iterator protocol specifies that the iteration ends with the return value `None` from `.next()` (or `.next_back()`) and it is unspecified what further calls return. The chain adaptor must account for this in its DoubleEndedIterator implementation. It uses three states: - Both `a` and `b` are valid - Only the Front iterator (`a`) is valid - Only the Back iterator (`b`) is valid The fourth state (neither iterator is valid) only occurs after Chain has returned None once, so we don't need to store this state. Fixes rust-lang#26316
|
Updated with a comment. If only one end of the iterator is used and everything is inlined, llvm should see that the state field only takes on two values (For example Both and Back), so it could behave like it did before. |
bors
added a commit
that referenced
this pull request
Aug 26, 2015
Correct iterator adaptor Chain The iterator protocol specifies that the iteration ends with the return value `None` from `.next()` (or `.next_back()`) and it is unspecified what further calls return. The chain adaptor must account for this in its DoubleEndedIterator implementation. It uses three states: - Both `a` and `b` are valid - Only the Front iterator (`a`) is valid - Only the Back iterator (`b`) is valid The fourth state (neither iterator is valid) only occurs after Chain has returned None once, so we don't need to store this state. Fixes #26316
|
Looks like one of the windows builders disappeared, but this passed tests everywhere (including windows) so merging manually. |
|
Thanks for the adjustment |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Correct iterator adaptor Chain
The iterator protocol specifies that the iteration ends with the return
value
Nonefrom.next()(or.next_back()) and it is unspecifiedwhat further calls return. The chain adaptor must account for this in
its DoubleEndedIterator implementation.
It uses three states:
aandbare valida) is validb) is validThe fourth state (neither iterator is valid) only occurs after Chain has
returned None once, so we don't need to store this state.
Fixes #26316