This package provides efficient alternating sequences based on finger trees. These can represent sequences made up of two types of element, e and a where two of the same type of element cannot follow each other directly.
Four different flavours are provided, isomorphic to ([(a, e)], a), ([(e, a)], e), [(a, e)], and [(e, a)].
Cons-like operations are O(1) amortised, and append operations are O(log(min(n, m))) amortised.
For more details, please see the Haddock documentation of Q4C12.TwoFinger.
q4c12-twofinger aims to be compatible with the most recent major version of GHC that was released over a year ago, and with all GHC major versions since. With GHC on a six-monthly release schedule, this will lead to each major release series of GHC receiving approximately eighteen months of support.