semigroupoids: Semigroupoids: Category sans id

[ bsd2, bsd3, comonads, control, library ] [ Propose Tags ]

Provides a wide array of (semi)groupoids and operations for working with them.

A Semigroupoid is a Category without the requirement of identity arrows for every object in the category.

A Category is any Semigroupoid for which the Yoneda lemma holds.

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. Applicative function composition forms a semigroupoid.

Similarly many structures are nearly a comonad, but not quite, for instance lists provide a reasonable extend operation in the form of tails, but do not always contain a value.

We describe the relationships between the type classes defined in this package and those from base (and some from contravariant) in the diagram below. Thick-bordered nodes correspond to type classes defined in this package; thin-bordered ones correspond to type classes from elsewhere. Solid edges indicate a subclass relationship that actually exists; dashed edges indicate a subclass relationship that should exist, but currently doesn't.

Apply, Bind, and Extend (not shown) give rise the Static, Kleisli and Cokleisli semigroupoids respectively.

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.


[Skip to Readme]
Versions [RSS] [faq] 1.0.0, 1.1.0, 1.1.1, 1.1.2, 1.1.3, 1.2.0, 1.2.1, 1.2.2, 1.2.2.1, 1.2.2.2, 1.2.2.3, 1.2.2.4, 1.2.4, 1.2.5, 1.2.6, 1.2.6.1, 1.2.6.2, 1.3, 1.3.1, 1.3.1.1, 1.3.1.2, 1.3.2, 1.3.2.1, 1.3.3, 1.3.4, 3.0, 3.0.0.1, 3.0.0.2, 3.0.1, 3.0.2, 3.0.3, 3.1, 4.0, 4.0.1, 4.0.2, 4.0.2.1, 4.0.3, 4.0.4, 4.2, 4.3, 4.5, 5, 5.0.0.1, 5.0.0.2, 5.0.0.3, 5.0.0.4, 5.0.1, 5.1, 5.2, 5.2.1, 5.2.2, 5.3, 5.3.1, 5.3.2, 5.3.3, 5.3.4, 5.3.5, 5.3.6 (info)
Change log CHANGELOG.markdown
Dependencies base (>=4.3 && <5), base-orphans (>=0.8.4 && <1), bifunctors (>=5.5.9 && <6), comonad (>=5.0.8 && <6), containers (>=0.3 && <0.7), contravariant (>=1.5.3 && <2), distributive (>=0.5.2 && <1), generic-deriving (==1.14.*), ghc-prim, hashable (>=1.2.5.0 && <1.4), semigroups (>=0.18.5 && <1), tagged (>=0.8.6.1 && <1), template-haskell (>=0.2.5.0), transformers (>=0.3 && <0.7), transformers-compat (>=0.5 && <0.8), unordered-containers (>=0.2.8.0 && <0.3), void (>=0.4 && <1) [details]
License BSD-2-Clause
Copyright Copyright (C) 2011-2015 Edward A. Kmett
Author Edward A. Kmett
Maintainer Edward A. Kmett <ekmett@gmail.com>
Revised Revision 1 made by ryanglscott at 2021-10-09T22:22:53Z
Category Control, Comonads
Home page http://github.com/ekmett/semigroupoids
Bug tracker http://github.com/ekmett/semigroupoids/issues
Source repo head: git clone git://github.com/ekmett/semigroupoids.git
Uploaded by ryanglscott at 2021-10-07T23:42:11Z
Distributions Arch:5.3.5, Debian:5.2.2, Fedora:5.3.5, FreeBSD:5.0.0.3, LTSHaskell:5.3.5, NixOS:5.3.5, Stackage:5.3.6, openSUSE:5.3.4
Downloads 274354 total (2944 in the last 30 days)
Rating 2.5 (votes: 8) [estimated by Bayesian average]
Your Rating
  • λ
  • λ
  • λ
Status Hackage Matrix CI
Docs available [build log]
Last success reported on 2021-10-07 [all 1 reports]

Modules

[Index] [Quick Jump]

Manual Flags

NameDescriptionDefault
containers

You can disable the use of the containers package using `-f-containers`.

Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

Enabled
contravariant

You can disable the use of the contravariant package using `-f-contravariant`.

Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

If disabled we will not supply instances of Contravariant

Enabled
distributive

You can disable the use of the distributive package using `-f-distributive`.

Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

If disabled we will not supply instances of Distributive

Enabled
comonad

You can disable the use of the comonad package using `-f-comonad`.

Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

If disabled we will not supply instances of Comonad

Enabled
tagged

You can disable the use of the tagged package using `-f-tagged`.

Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

Enabled
unordered-containers

You can disable the use of the `unordered-containers` package (and also its dependency hashable) using `-f-unordered-containers`.

Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

Enabled
Automatic Flags
NameDescriptionDefault

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

Downloads

Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.

Maintainer's Corner

For package maintainers and hackage trustees

Candidates


Readme for semigroupoids-5.3.6

[back to package description]

semigroupoids

Hackage Build Status

A semigroupoid is a Category without id. This package provides a range of id-free versions of type classes, as well as some supporting functions and data types.

Field Guide

The diagram below describes the relationships between the type classes defined in this package, and those from base (with some from contravariant as well). Thick-bordered nodes correspond to type classes defined in this package; thin-bordered ones are from elsewhere. Solid edges represent subclass relationships that actually exist; dashed edges are those which should exist in theory.

A diagram of the relationships between type classes defined in this package and elsewhere.

We also provide the following table. This is structured in superclass order - thus, for any type class T, all superclasses of T will be listed before T in the table.

Name Location Superclass of Ideally superclass of
Functor base Alt, Apply, Traversable
Foldable base Traversable, Foldable1
Bifunctor base Biapply
Contravariant base Divise, Decide
Semigroupoid semigroupoids Category
Alt semigroupoids Plus
Apply semigroupoids Bind Applicative
Traversable base Traversable1
Foldable1 semigroupoids Traversable1
Biapply semigroupoids
Divise semigroupoids Divisible
Decide semigroupoids Conclude Decidable
Category base Arrow
Plus semigroupoids Alternative
Applicative base Alternative, Monad
Bind semigroupoids Monad
Traversable1 semigroupoids
Divisible contravariant
Conclude semigroupoids Decidable
Arrow base
Alternative base MonadPlus
Monad base MonadPlus
Decidable contravariant
MonadPlus base

We omit some type class relationships from this diagram, as they are not relevant for the purposes of this package.

Contact Information

Contributions and bug reports are welcome!

Please feel free to contact me through Github or on the #haskell IRC channel on LiberaChat.

-Edward Kmett