They are basically the same. As per the documentation:

paste0(..., collapse) is equivalent to paste(..., sep = "", collapse), slightly more efficiently.

I assume you mean that i % 2 returns -1 for negative odd numbers whereas i & 1 is positive. But I fail to see where behavior is different for even numbers. See https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=1ba4abb31460c86f5c426d188672c5bb

It may also be worth adding that this is a good test for unsigned integers, but will not work in general for signed integers when using rust. Since len() always returns a positive number (usize) this is a safe test in the above code.

If you're trying to test odd/even for something that could be positive or negative, the n % 2 == 0 test is a better choice.

It does a bitwise AND. As all odd numbers will have the final bit set and all even numbers not, this is a good test.

These methods are lazy.

@newmaidumosa sorry for long reply. that's good question, but i've never used it before. you can define them directly

Fixed

here. comments visible, and links to the solution page. The code itself isn't visible, but all comments that aren't flagged are readable

and I wish you could think about the spoiler flag... ;p

If you guess a few things you can figure out how to transform them directly :

-if there is no number part then ...
-if there is just one latter then ...

IIUC it's basically 'does not cheat by importing the reference solution'.

If you are failing that test and you think your code is legitimate, put your code here in a 'spoiler' comment and raise as an issue.

Initial value for foldr. You have to fill in something, and it must be able to be any type for the whole thing to typecheck. It is then thrown away because const discards its second argument unevaluated. :]

thanks)))

I’m happy to help