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The native binary operators aren't a three way compare though.

The author seems to assume nobody needs a three way compare, which I feel is assuming a bit too much.

In particular because it is there because someone is using/needing it already.

Basically their comment actually says that everyone who does need a three way compare should just re-implement what they wrote there (and maybe they'll make sure everyone's code is optimized later). Sounds pretty bizarre to me to discourage code reuse. And if three way compares are a pattern they want to discourage in the first place it should be elaborated on in documentation.