Go deh!: Sparse Ranges

A developer built a `sparse_range` abstraction in Python that allows punching holes in integer ranges without memory overhead. Inspired by a Python Discuss thread, the implementation uses `RangePointer` objects that track inclusion and exclusion ranges, supporting both forward and backward traversal via a mathematical range-reversal formula. The design is validated with a declarative Sieve of Eratosthenes that uses pure arithmetic progressions as exclusion streams instead of a mutable boolean array, passing both forward and backward traversal tests. Gemini AI assisted with implementation details throughout the project.