Copyright	(C) 2011-2015 Edward Kmett
License	BSD-style (see the file LICENSE)
Maintainer	Edward Kmett <ekmett@gmail.com>
Stability	provisional
Portability	portable
Safe Haskell	Safe
Language	Haskell98

Data.Functor.Extend

Contents

Description

Synopsis

Extendable Functors

There are two ways to define an Extend instance:

I. Provide definitions for extended satisfying this law:

extended f . extended g = extended (f . extended g)

II. Alternately, you may choose to provide definitions for duplicated satisfying this law:

duplicated . duplicated = fmap duplicated . duplicated

You may of course, choose to define both duplicated and extended. In that case you must also satisfy these laws:

extended f = fmap f . duplicated
duplicated = extended id

These are the default definitions of extended and duplicated.

class Functor w => Extend w where Source

Minimal complete definition

Methods

duplicated :: w a -> w (w a) Source

duplicated = extended id
fmap (fmap f) . duplicated = duplicated . fmap f

extended :: (w a -> b) -> w a -> w b Source

extended f  = fmap f . duplicated

Instances

Extend [] Source
Extend Identity Source
Extend Maybe Source
Extend Tree Source
Extend Seq Source
Extend NonEmpty Source
Semigroup m => Extend ((->) m) Source
Extend (Either a) Source
Extend ((,) e) Source
Extend w => Extend (IdentityT w) Source
Extend f => Extend (MaybeApply f) Source
(Extend w, Semigroup m) => Extend (TracedT m w) Source
Extend w => Extend (StoreT s w) Source
Extend w => Extend (EnvT e w) Source
(Extend f, Extend g) => Extend (Sum f g) Source
(Extend f, Semigroup a) => Extend (Static f a) Source