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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.
foldRight / fold with a summing operation is identical to just using sum fun. This is distracting and misleading to any reader, also why do you care about folding from the right?
Plus: folding with summing and an initial value of 0 is identical to reduce... :-)