walrus. neat.

Haskell ->
This kata was confusing and there's a discrepancy between the description and the test cases. The description says:

-- The following are some examples of how this class is used:
-- collection = ['a','b','c','d','e','f']
-- itemsPerPage = 4
...
-- pageIndex collection itemsPerPage (-20) shouldBe Nothing

but the automated test cases require negative pageIndex item = Just 0

Took me hours to figure out what was going on because of Haskell's terse error messages.