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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