Copyright | (C) 2012-2016 Nicolas Frisby, (C) 2015-2016 Ryan Scott |
---|---|
License | BSD-style (see the file LICENSE) |
Maintainer | Ryan Scott |
Portability | Portable |
Safe Haskell | None |
Language | Haskell98 |
Haskell98 invariant functors (also known as exponential functors).
For more information, see Edward Kmett's article "Rotten Bananas":
- class Invariant f where
- invmapFunctor :: Functor f => (a -> b) -> (b -> a) -> f a -> f b
- genericInvmap :: (Generic1 f, Invariant (Rep1 f)) => (a -> b) -> (b -> a) -> f a -> f b
- newtype WrappedFunctor f a = WrapFunctor {
- unwrapFunctor :: f a
- invmapContravariant :: Contravariant f => (a -> b) -> (b -> a) -> f a -> f b
- newtype WrappedContravariant f a = WrapContravariant {
- unwrapContravariant :: f a
- class Invariant2 f where
- invmap2Bifunctor :: Bifunctor f => (a -> c) -> (c -> a) -> (b -> d) -> (d -> b) -> f a b -> f c d
- newtype WrappedBifunctor k k1 p a b :: forall k k1. (k -> k1 -> *) -> k -> k1 -> * = WrapBifunctor {
- unwrapBifunctor :: p a b
- invmap2Profunctor :: Profunctor f => (a -> c) -> (c -> a) -> (b -> d) -> (d -> b) -> f a b -> f c d
- newtype WrappedProfunctor p a b = WrapProfunctor {
- unwrapProfunctor :: p a b
Invariant
class Invariant f where Source #
Any * -> *
type parametric in the argument permits an instance of
Invariant
.
Instances should satisfy the following laws:
invmap id id = id invmap f2 f2' . invmap f1 f1' = invmap (f2 . f1) (f1' . f2')
invmap :: (a -> b) -> (b -> a) -> f a -> f b Source #
invmap :: (Generic1 f, Invariant (Rep1 f)) => (a -> b) -> (b -> a) -> f a -> f b Source #
invmapFunctor :: Functor f => (a -> b) -> (b -> a) -> f a -> f b Source #
GHC.Generics
With GHC 7.2 or later, Invariant
instances can be defined easily using GHC
generics like so:
{-# LANGUAGE DeriveGeneric, FlexibleContexts #-}
import Data.Functor.Invariant
import GHC.Generics
data T f a = T (f a) deriving Generic1
instance Invariant f => Invariant
(T f)
Be aware that generic Invariant
instances cannot be derived for data types
that have function arguments in which the last type parameter appears in a
position other than the result type (e.g., data Fun a = Fun (a -> a)
). For
these, you can derive them using the Data.Functor.Invariant.TH module.
genericInvmap :: (Generic1 f, Invariant (Rep1 f)) => (a -> b) -> (b -> a) -> f a -> f b Source #
A generic implementation of invmap
.
newtype WrappedFunctor f a Source #
WrapFunctor | |
|
Monad m => Monad (WrappedFunctor * m) Source # | |
Functor f => Functor (WrappedFunctor * f) Source # | |
Applicative f => Applicative (WrappedFunctor * f) Source # | |
Foldable f => Foldable (WrappedFunctor * f) Source # | |
Traversable f => Traversable (WrappedFunctor * f) Source # | |
Alternative f => Alternative (WrappedFunctor * f) Source # | |
MonadPlus m => MonadPlus (WrappedFunctor * m) Source # | |
Functor f => Invariant (WrappedFunctor * f) Source # | |
Eq (f a) => Eq (WrappedFunctor k f a) Source # | |
Ord (f a) => Ord (WrappedFunctor k f a) Source # | |
Read (f a) => Read (WrappedFunctor k f a) Source # | |
Show (f a) => Show (WrappedFunctor k f a) Source # | |
invmapContravariant :: Contravariant f => (a -> b) -> (b -> a) -> f a -> f b Source #
Every Contravariant
functor is also an Invariant
functor.
newtype WrappedContravariant f a Source #
Wrap a Contravariant
functor to be used as a member of Invariant
.
Divisible f => Divisible (WrappedContravariant * f) Source # | |
Decidable f => Decidable (WrappedContravariant * f) Source # | |
Contravariant f => Contravariant (WrappedContravariant * f) Source # | |
Contravariant f => Invariant (WrappedContravariant * f) Source # | |
Eq (f a) => Eq (WrappedContravariant k f a) Source # | |
Ord (f a) => Ord (WrappedContravariant k f a) Source # | |
Read (f a) => Read (WrappedContravariant k f a) Source # | |
Show (f a) => Show (WrappedContravariant k f a) Source # | |
Invariant2
class Invariant2 f where Source #
Any * -> * -> *
type parametric in both arguments permits an instance of
Invariant2
.
Instances should satisfy the following laws:
invmap2 id id id id = id invmap2 f2 f2' g2 g2' . invmap2 f1 f1' g1 g1' = invmap2 (f2 . f1) (f1' . f2') (g2 . g1) (g1' . g2')
Invariant2 (->) Source # | |
Invariant2 Either Source # | |
Invariant2 (,) Source # | |
Invariant2 Arg Source # | from Data.Semigroup |
Invariant2 Op Source # | from the |
Invariant2 (K1 i) Source # | from GHC.Generics |
Invariant2 ((,,) a) Source # | |
Arrow arr => Invariant2 (WrappedArrow arr) Source # | from Control.Applicative |
Monad m => Invariant2 (Kleisli m) Source # | from Control.Arrow |
Invariant2 (Const *) Source # | from Control.Applicative |
Comonad w => Invariant2 (Cokleisli w) Source # | from the |
Invariant2 p => Invariant2 (Codensity p) Source # | from the |
Invariant2 p => Invariant2 (CofreeMapping p) Source # | from the |
Invariant2 (FreeMapping p) Source # | from the |
Invariant2 p => Invariant2 (CofreeTraversing p) Source # | from the |
Invariant2 (FreeTraversing p) Source # | from the |
Invariant2 p => Invariant2 (TambaraSum p) Source # | from the |
Invariant2 (PastroSum p) Source # | from the |
Invariant2 (CotambaraSum p) Source # | from the |
Invariant2 (CopastroSum p) Source # | from the |
Invariant2 p => Invariant2 (Closure p) Source # | from the |
Invariant2 (Environment p) Source # | from the |
Invariant2 p => Invariant2 (Tambara p) Source # | from the |
Invariant2 (Pastro p) Source # | from the |
Invariant2 (Cotambara p) Source # | from the |
Invariant f => Invariant2 (Star f) Source # | from the |
Invariant f => Invariant2 (Costar f) Source # | from the |
Arrow arr => Invariant2 (WrappedArrow arr) Source # | from the |
Invariant2 (Forget r) Source # | from the |
Invariant2 (Tagged *) Source # | from the |
Invariant2 (Constant *) Source # | from the |
Invariant2 ((,,,) a b) Source # | |
(Invariant2 p, Invariant2 q) => Invariant2 (Ran p q) Source # | from the |
(Invariant2 p, Invariant2 q) => Invariant2 (Procompose p q) Source # | from the |
(Invariant2 p, Invariant2 q) => Invariant2 (Rift p q) Source # | from the |
(Invariant f, Invariant2 p) => Invariant2 (Cayley f p) Source # | from the |
Invariant2 ((,,,,) a b c) Source # | |
Bifunctor p => Invariant2 (WrappedBifunctor * * p) Source # | from the |
Invariant g => Invariant2 (Joker * * g) Source # | from the |
Invariant2 p => Invariant2 (Flip * * p) Source # | from the |
Invariant f => Invariant2 (Clown * * f) Source # | from the |
Profunctor p => Invariant2 (WrappedProfunctor * * p) Source # | |
(Invariant2 f, Invariant2 g) => Invariant2 (Product * * f g) Source # | from the |
(Invariant2 p, Invariant2 q) => Invariant2 (Sum * * p q) Source # | from the |
(Invariant f, Invariant2 p) => Invariant2 (Tannen * * * f p) Source # | from the |
(Invariant2 p, Invariant f, Invariant g) => Invariant2 (Biff * * * * p f g) Source # | from the |
invmap2Bifunctor :: Bifunctor f => (a -> c) -> (c -> a) -> (b -> d) -> (d -> b) -> f a b -> f c d Source #
Every Bifunctor
is also an Invariant2
functor.
newtype WrappedBifunctor k k1 p a b :: forall k k1. (k -> k1 -> *) -> k -> k1 -> * #
WrapBifunctor | |
|
Bifunctor p => Bifunctor (WrappedBifunctor * * p) | |
Biapplicative p => Biapplicative (WrappedBifunctor * * p) | |
Bitraversable p => Bitraversable (WrappedBifunctor * * p) | |
Bifoldable p => Bifoldable (WrappedBifunctor * * p) | |
Bifunctor p => Invariant2 (WrappedBifunctor * * p) Source # | from the |
Bifunctor p => Functor (WrappedBifunctor * * p a) | |
Bifoldable p => Foldable (WrappedBifunctor * * p a) | |
Bitraversable p => Traversable (WrappedBifunctor * * p a) | |
Generic1 (WrappedBifunctor k * p a) | |
Bifunctor p => Invariant (WrappedBifunctor * * p a) Source # | from the |
Eq (p a b) => Eq (WrappedBifunctor k k1 p a b) | |
Ord (p a b) => Ord (WrappedBifunctor k k1 p a b) | |
Read (p a b) => Read (WrappedBifunctor k k1 p a b) | |
Show (p a b) => Show (WrappedBifunctor k k1 p a b) | |
Generic (WrappedBifunctor k k1 p a b) | |
type Rep1 (WrappedBifunctor k * p a) | |
type Rep (WrappedBifunctor k k1 p a b) | |
invmap2Profunctor :: Profunctor f => (a -> c) -> (c -> a) -> (b -> d) -> (d -> b) -> f a b -> f c d Source #
Every Profunctor
is also an Invariant2
functor.
newtype WrappedProfunctor p a b Source #
Wrap a Profunctor
to be used as a member of Invariant2
.
WrapProfunctor | |
|