On 9/9/19 12:43 AM, Hans Dembinski via Boost wrote:

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On 5. Sep 2019, at 17:52, Bjorn Reese via Boost wrote:

I am working on a circular queue library that contains a non-owning circular span, a fixed-sized circular array, and a dynamically resizable circular vector.

It looks like circular span can adapt any suitable STL container into a circular one. In fact, circular array and vector are implemented by inheriting privately from std::array and circular::span, which is nice. However, wouldn't it be more general to provide a circular_adaptor, which works with any vector or array, and perhaps even any STL container? Perhaps someone wants a circular set?

FYI - I used such a library as an example in my CppCon Talk about how to write documentation for a C++ library: https://www.youtube.com/watch?v=YxmdCxX9dMk&t=3s The talk was about documentation, but as a side effect produced a library component similar to the above. If any one want's to make use of this - fine by me. One benefit would be that he who programs wouldn't have to write documentation - it's already done!

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Would you be interested in adding such a library to Boost?

The design is inspired by Boost.CircularBuffer, std::span, and P0059R4 std::experimental::ring_span.

The code can be found at:

https://github.com/breese/trial.circular

The documentation can be found at:

https://github.com/breese/trial.circular/tree/develop/doc

This is the source, the renderable documentation is here:

https://github.com/breese/trial.circular/blob/develop/doc/circular.adoc

The rationale is short, I would like to know why I should use this instead of boost.circular_buffer.

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On 10. Sep 2019, at 01:32, Gavin Lambert via Boost wrote:

On 9/09/2019 19:43, Hans Dembinski wrote:

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It looks like circular span can adapt any suitable STL container into a circular one. In fact, circular array and vector are implemented by inheriting privately from std::array and circular::span, which is nice. However, wouldn't it be more general to provide a circular_adaptor, which works with any vector or array, and perhaps even any STL container? Perhaps someone wants a circular set?

I'm curious what you mean by that.

Circularity implies the ability to do random indexing (on the underlying container, even if hiding this from consumers), thus it should in principle be compatible with any container that produces random access iterators -- including array and vector, but not including set.

How would you imagine a "circular set" working?

It probably doesn't make much sense. I didn't really think a lot about it, but in my defence, there are set implementations with random access iterators, namely boost::flat_set. https://www.boost.org/doc/libs/1_71_0/doc/html/boost/container/flat_set.html The main point of my suggestion was rather (as explained in a private email to Bjorn), that it may be better if the convenience classes circular::vector and circular::array are not hard-wired to use std::vector and std::array, but that the adapted container is a template parameter. There are other vector and array implementations that people may want to use, boost::vector and boost::static_vector come to mind. The circular::vector template could look like this: template class vector : private AdaptedContainer, private circular::span<T> { … }