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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
updated description !
I agree. this is very poorly written.
That's haskell translator's doing and shouldn't be there for reasons mentioned above.
I don't see any mention of negative numbers in the description nor it's tested in other languages, additionally persistent sign isn't obvious as
f(-1) == 1could also be a valid interpretation.