Create `suffixes` Function on List

Question

I wrote the following suffixes function. Given a list, it returns the list + all sub-lists.

suffixes [1,2,3,4] == [[1,2,3,4], [2,3,4], [3,4], [4], []]

Please critique my implementation.

suffixes :: [a] -> [[a]]
suffixes [] = [] : []
suffixes xxs@(_:xs) = xxs : suffixes xs

Answer 1

Looks good to me. The only thing I would change is

suffixes [] = [] : []

to

suffixes [] = [[]]

as it's a bit more readable.

When re-inventing functions, it can be instructive to look up their definition using Hoogle. Following the links, we find this definition in Data.List:

tails :: [a] -> [[a]]
tails xs = xs : case xs of
 [] -> []
 _ : xs' -> tails xs'

• Kevin Meredith: Thank you for your continued help on most/all of my recent questions.
• mjolka: @KevinMeredith my pleasure. I thoroughly enjoyed the previous one (Streams) in particular :)