AFAIK, it's because i64 implements the trait Ord, which contains those methods.

sorry for necro-replying

Can you comment on my solution, which benchmarks around 4 times faster than either yours or OP's solution? I tried to avoid iterating over anything more than once, and to avoid allocations where possible

The Rust translation doesn't have random tests

If Rust has random tests, then close the issue please.

No, everything works correctly now. I just had to fix the number of seconds in a year I was using

The other problem remains, right?

I just realized it was because I calculated a year as 365.25 days, not 365... God, I really should've paid more attention to the detailed explanation.

If the input for that test is 132030240, then the expected answer is right.

Actually, generally accepted best practice is to not use named lambdas. Lambdas should be 'throw away' expressions, not statements and def fn's will usually eek out performance over λ expressions but not by anything really noticeable unless you have some order of op stuff going on. If you really want to make this fn sing, use a generator, ala my fork.

using a lambda, an "anonymous function" to make a named function is sooOoOOoOOooOooOooOo smart and definitely not bad practices. Most linters will yell at you for this.