| Copyright | (C) 2011 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
- class Functor w => Extend w where
- duplicated :: w a -> w (w a)
- extended :: (w a -> b) -> w a -> w b
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
Nothing
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 [] | |
| Extend Maybe | |
| Extend Identity | |
| Extend Tree | |
| Extend Seq | |
| Extend NonEmpty | |
| Semigroup m => Extend ((->) m) | |
| Extend (Either a) | |
| Extend ((,) e) | |
| Extend w => Extend (IdentityT w) | |
| Extend f => Extend (MaybeApply f) | |
| (Extend f, Extend g) => Extend (Coproduct f g) | |
| (Extend w, Semigroup m) => Extend (TracedT m w) | |
| Extend w => Extend (StoreT s w) | |
| Extend w => Extend (EnvT e w) | |
| (Extend f, Semigroup a) => Extend (Static f a) |