REQ sketch

[pmcgleenon]

Hello

thanks for creating this project!

There is a rust implementation of Relative Error Quantiles sketch derived from the C++ apache datasketches reference here https://github.com/pmcgleenon/reqsketch-rs

Maybe it could be used as a starting point for a REQ implementation in this project, it would need changes for the serialization and maybe other areas as well as a careful review

What do you think about adapting this existing rust implementation, or do you think a fresh start would be better?

[tisonkun]

@pmcgleenon either is OK for me.

To reduce review burden, I'd prefer a version as closed to the C++ impl as possible. The patch would better note any significant changes from the C++ or other referenced impl. Then we can use that as a starting point to make more changes.

You can take the commit history of CpcSketch as an example.

And yes, keep the serde impl compatible with other impl is significant since datasketches work hard to make all sketches interoperable among languages.