paulirwin commented on issue #279:
URL: https://github.com/apache/lucenenet/issues/279#issuecomment-2455506582
I looked into the remaining types a little bit, and none of them map cleanly
to `IEnumerable<T>`, unless we wanted to add an _additional_ `IEnumerable<T>`
interface to them instead of trying to replace their Iterator-ness.
## DocIdSetIterator (and all of its subclasses)
Apart from the monumental amount of work here if we were to change this
design in a breaking way (with well over 100 derived types), DocIdSetIterator
is perhaps the closest of the three remaining types to being able to cleanly
map to `IEnumerable<T>`. `NextDoc()` maps pretty cleanly to the
`IEnumerator<int>` pattern. I think our best path is going to be adding
`IEnumerable<T>` here in a non-breaking way, rather than trying to change the
existing implementation. That way, anyone that wants to enumerate over it may
do so, but the existing methods are not affected.
A quick implementation on DocIdSetIterator might look like:
```c#
public IEnumerator<int> GetEnumerator() => new DocIdSetEnumerator(this);
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
private class DocIdSetEnumerator : IEnumerator<int>
{
private readonly DocIdSetIterator outerInstance;
private int current;
public DocIdSetEnumerator(DocIdSetIterator outerInstance)
{
this.outerInstance = outerInstance;
current = -1;
}
public int Current => current;
object IEnumerator.Current => current;
public void Dispose()
{
}
public bool MoveNext()
{
current = outerInstance.NextDoc();
return current != NO_MORE_DOCS;
}
public void Reset()
{
throw new System.NotSupportedException();
}
}
```
This way, all subclasses will automatically inherit this behavior.
If that design sounds good, I can get a PR for that.
## CharArrayIterator
I believe this type is what was referred to as `CharacterIterator` in
@NightOwl888's last post from 2020, but let me know if I'm wrong. This type
supports bidirectional iteration, and I think there is a nice symmetry
currently with `Next` and `Previous`. I don't think it's a good idea for us to
change this to support `IEnumerable<char>`, although again I could see adding
an implementation similar to the one above for DocIdSetIterator that just calls
`Next` on the CharArrayIterator.
## BreakIterator
I'm assuming this is referring to BreakIterator in ICU4N, in which case that
should be an issue there, although similarly to CharArrayIterator, it has a
nice bidirectional symmetry currently. I think we should keep its existing
design, and just consider adding `IEnumerable<int>` to it in a non-breaking way.
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