Scan documentation is poor

[Boarders]

The documentation for scanl was probably taken straight from Data.List but is a little confusing in the context of Text (I also am not very clear on whether scans make much sense but that is above my pay grade):

-- | /O(n)/ 'scanl' is similar to 'foldl', but returns a list of
-- successive reduced values from the left.
-- Performs replacement on invalid scalar values.
--
-- > scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]
--
-- Note that
--
-- > last (scanl f z xs) == foldl f z xs.

[Boarders]

Maybe this is not a problem as it is clearly conceptual, I'm not sure - could be worth adding a comment.

[Bodigrim]

One needs to clarify, whether replacement of invalid scalar values (safe) happens in between of successive applications of f or only afterwards.

[Justbeth22]

One needs to clarify, whether replacement of invalid scalar values (safe) happens in between of successive applications of f or only afterwards.