Selective applicative functors: declare your effects statically, select
which to execute dynamically.

This is a library for selective applicative functors, or just selective
functors for short, an abstraction between applicative functors and monads,
introduced in this paper:

    https://dl.acm.org/doi/10.1145/3341694

Homepage:
http://hackage.haskell.org/package/selective
