[0x457]

Why? You can just adapt/use https://github.com/redis/redis/blob/unstable/src/hyperloglog...

Why does it need to be pure C? There are C++ implementations. It's an algorithm not a social media app, it doesn't need to be updated once a week, C also not node.js - it doesn't break compatibility every release. What is wrong with these 10+ years touched ones?

Even the redis version of HLL isn't updated all that often.

[simonw]

That's exactly what I'm arguing for here: it would be useful if Redis data structures like that were available to be easily embedded in other programs.

"You can just adapt X from Redis" is the whole point of this hypothetical.