fixing issue 22 : unset iterators

[lemire]

Fixes #22

[Copilot]

Pull Request Overview

This PR adds support for iterating over unset bits in a bitmap within a specified range. The implementation provides a new UnsetIterator method that returns values in [min, max] that are NOT contained in the bitmap, along with a helper Unset function for use with Go 1.23+ range-over-function.

Key changes:

• Added unsetIterator type with logic to iterate over unset values within a range
• Added Bitmap.UnsetIterator(min, max) method to create the iterator
• Added Unset(b, min, max) function for Go 1.23+ range-over-function support
• Comprehensive test coverage for various edge cases

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
roaring.go	Implements unsetIterator struct and UnsetIterator method to iterate over unset bits in a range
iter.go	Adds Unset function for Go 1.23+ range-over-function support
iter_test.go	Comprehensive tests covering empty bitmaps, sparse bitmaps, edge cases, and early termination

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[rogpeppe]

It would be helpful if this returned IntPeekable. That would make it possible to iterate over all ranges efficiently (see #491 ). Maybe there's another way of doing that that I haven't thought of though?

[lemire]

It would be helpful if this returned IntPeekable

Ok. Done.

[rogpeppe]

Thanks for adding the Peekable capability.

One passing thought after playing with this: it's arguably slightly confusing that this API call uses a uint32 closed range where other calls in the API (e.g. Flip, RemoveRange, etc) use a uint64 closed range. I don't see any other examples in the API where a range is specified as a uint32 closed range, so in the interests of consistency I'd suggest using a uint64 open range for UnsetIterator too.

Also it often simplifies code to be able to use a zero-length interval without special-casing, which isn't possible with this API in general - specifically I don't think there's any way to specify a zero-length interval at the very start, because [0, -1] isn't possible with uint32.

[lemire]

@rogpeppe Given that this is a new feature, we can break the API now. Feel free to issue a pull request.

We can introduce breaking changes at this point.

[rogpeppe]

@rogpeppe Given that this is a new feature, we can break the API now. Feel free to issue a pull request.

We can introduce breaking changes at this point.

sure: #500