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nevans
added this pull request to stack #775
October 3, 2026 22:32
This changes a `SequenceSet#slice` to return an empty set (rather than `nil`) in the same circumstance. This mimics `Array#slice`, which returns an empty array when starting at the array's size (immediately after the last index). Note that `SequenceSet#slice` indexes the monotonic set numbers, so `#cardinality` is used instead of `#size` (which measures the ordered list data). This could be seen as a minor breaking change. But I'm treating it as a bugfix because: * `SequenceSet#slice` was always intended to mimic `Array#slice`. * The documented API doesn't change, it still returns `nil` or a set. * `SequenceSet#slice` already returns an empty set sometimes. So, I think it's unlikely there is much code that depends on this bug. And any code that _does_ depend on it is (arguably) buggy already, and should be easy to fix. Please note that this is done as a minimal change to avoid refactoring the underlying slice implementation. Since `#cardinality` isn't cached, this currently requires scanning every set element a second time, which is _very_ inefficient for large sets. Fixing `SequenceSet#slice` performance is what led to finding and fixing this bug in the first place. But, for now I'm prioritizing fixing and testing `#slice`'s behavior, even if that leads to some reduced performance in cases like this.
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This changes a
SequenceSet#sliceto return an empty set (rather thannil) in the same circumstance. This mimicsArray#slice, which returns an empty array when starting at the array's size (immediately after the last index). Note thatSequenceSet#sliceindexes the monotonic set numbers, so#cardinalityis used instead of#size(which measures the ordered list data).This could be seen as a minor breaking change. But I'm treating it as a bug fix because:
SequenceSet#slicewas always intended to mimicArray#slice.nilor a set.SequenceSet#slicealready returns an empty set sometimes.So, I think it's unlikely there is much (or any) code that depends on this bug. And any code that does depend on it is (arguably) buggy already, and should be easy to fix.