Very interesting, this is the first time I hear about segmented iterators and hierarchical algorithms.

I faced a similar issue myself when implementing a chunked vector a la `std::deque`, but opted for callback-based internal iteration, i.e.

    void ChunkedVector::forEach(auto&& f)
    {
        for (auto& chunk : chunks)
            for (auto& item : chunk) 
                if (f(item) == ControlFlow::Break)
                    return;
    }

Where `ControlFlow` is just:

    enum class [[nodiscard]] ControlFlow : bool
    {
        Continue,
        Break
    };

This is massively simpler to implement, and can model simpler algorithms such as `for_each`, `fill`, `transform`, `count`, `accumulate`.

It's sometimes inferior in terms of ergonomics, and cannot express more complicated algorithms or iteration patterns (e.g. partial range, going backwards), but so far it has served me well.

Just something to consider if implementation simplicity is the priority and there's no need for a very generic suite of algorithms.