functor-apply: Applicative sans pure, Monad sans return, Alternative sans empty

[ bsd3, control, deprecated, library ] [ Propose Tags ]
Deprecated. in favor of semigroupoids

Provides a wide array of semigroup based Functors.

When working with comonads you often have the <*> portion of an Applicative, but not the pure. This was captured in Uustalu and Vene's "Essence of Dataflow Programming" in the form of the ComonadZip class in the days before Applicative. Apply provides a weaker invariant, but for the comonads used for data flow programming (found in the streams package), this invariant is preserved.


Functor -> Apply -------> Bind
 |           |             |
 v           v             v
Alt     Applicative ---> Monad
 |           |             |
 v           v             v
Plus -> Alternative -> MonadPlus

This lets us remove many of the restrictions from various monad transformers as in many cases the binding operation or <*> operation does not require them.

Finally, to work with these weaker structures it is beneficial to have containers that can provide stronger guarantees about their contents, so versions of Traversable and Foldable that can be folded with just a Semigroup are added.

Versions [faq] 0.5.0, 0.6.0, 0.7.0, 0.7.1, 0.7.2, 0.7.3, 0.7.4,, 0.9.0, 0.9.1, 0.9.2, 0.9.3, 0.10.0,,,, 0.10.1, 0.10.3, 0.10.4, 0.10.5, 0.11
Dependencies base (>=4 && <4.4), comonad (>=0.9.0 && <1.0), containers (>=0.4.0 && <0.5), semigroups (>=0.3.2 && <0.4), transformers (>=0.2.0 && <0.3) [details]
License BSD-3-Clause
Copyright Copyright (C) 2011 Edward A. Kmett
Author Edward A. Kmett
Maintainer Edward A. Kmett <>
Category Control, Comonads
Home page
Uploaded by EdwardKmett at 2011-01-29T12:15:55Z
Distributions NixOS:0.11
Downloads 15269 total (25 in the last 30 days)
Rating (no votes yet) [estimated by Bayesian average]
Your Rating
  • λ
  • λ
  • λ
Status Hackage Matrix CI
Docs uploaded by user
Build status unknown [no reports yet]




Maintainer's Corner

For package maintainers and hackage trustees