Options.Harg.Het.Variant

Documentation

data VariantF (xs :: [(Type -> Type) -> Type]) (f :: Type -> Type) where

A Variant is similar to nested Eithers. For example, Variant '[Int, Bool, Char] is isomorphic to Either Int (Either Bool Char). VariantF is a variant for higher-kinded types, which means that the type-level list holds types of kind (Type -> Type) -> Type, and the second parameter is the type constructor f :: Type -> Type. To pattern match on a variant, HereF and ThereF can be used:

  getFromVariant :: Variant '[Int, Bool, String] -> Bool
  getFromVariant (ThereF (HereF b)) = b

Constructors

HereF :: x f -> VariantF (x ': xs) f

ThereF :: VariantF xs f -> VariantF (y ': xs) f

Instances

(TraversableB x, TraversableB (VariantF xs)) => TraversableB (VariantF (x ': xs) :: (Type -> Type) -> Type)

Defined in Options.Harg.Het.Variant

Methods

btraverse :: Applicative t => (forall (a :: k). f a -> t (g a)) -> VariantF (x ': xs) f -> t (VariantF (x ': xs) g)

TraversableB (VariantF ([] :: [(Type -> Type) -> Type]))

Defined in Options.Harg.Het.Variant

Methods

btraverse :: Applicative t => (forall (a :: k). f a -> t (g a)) -> VariantF [] f -> t (VariantF [] g)

(FunctorB x, FunctorB (VariantF xs)) => FunctorB (VariantF (x ': xs) :: (Type -> Type) -> Type)

Defined in Options.Harg.Het.Variant

Methods

bmap :: (forall (a :: k). f a -> g a) -> VariantF (x ': xs) f -> VariantF (x ': xs) g

FunctorB (VariantF ([] :: [(Type -> Type) -> Type]))

Defined in Options.Harg.Het.Variant

Methods

bmap :: (forall (a :: k). f a -> g a) -> VariantF [] f -> VariantF [] g

Helpers for pattern-matching on variants

pattern In1 :: x1 f -> VariantF (x1 ': xs) f

pattern In2 :: x2 f -> VariantF (x1 ': (x2 ': xs)) f

pattern In3 :: x3 f -> VariantF (x1 ': (x2 ': (x3 ': xs))) f

pattern In4 :: x4 f -> VariantF (x1 ': (x2 ': (x3 ': (x4 ': xs)))) f

pattern In5 :: x5 f -> VariantF (x1 ': (x2 ': (x3 ': (x4 ': (x5 ': xs))))) f

type family FoldSignatureF (xs :: [(Type -> Type) -> Type]) r f where ...

Create the signature needed for FromVariantF to work. This constructs a function that takes as arguments functions that can act upon each item in the list that the VariantF holds. For example, VariantF [a, b, c] f will result to the signature:

  VariantF [a, b, c] f -> (a f -> r) -> (b f -> r) -> (c f -> r) -> r

Equations

FoldSignatureF (x ': xs) r f = (x f -> r) -> FoldSignatureF xs r f

FoldSignatureF '[] r f = r

class FromVariantF xs result f where

Methods

fromVariantF :: VariantF xs f -> FoldSignatureF xs result f

Instances

(tail ~ (x' ': xs), FromVariantF tail result f, IgnoreF tail result f) => FromVariantF (x ': (x' ': xs)) result f

Defined in Options.Harg.Het.Variant

Methods

fromVariantF :: VariantF (x ': (x' ': xs)) f -> FoldSignatureF (x ': (x' ': xs)) result f

FromVariantF (x ': ([] :: [(Type -> Type) -> Type])) result f

Defined in Options.Harg.Het.Variant

Methods

fromVariantF :: VariantF (x ': []) f -> FoldSignatureF (x ': []) result f

class IgnoreF (args :: [(Type -> Type) -> Type]) result f where

Methods

ignoreF :: result -> FoldSignatureF args result f

Instances

IgnoreF ([] :: [(Type -> Type) -> Type]) result f

Defined in Options.Harg.Het.Variant

Methods

ignoreF :: result -> FoldSignatureF [] result f

IgnoreF xs result f => IgnoreF (x ': xs) result f

Defined in Options.Harg.Het.Variant

Methods

ignoreF :: result -> FoldSignatureF (x ': xs) result f

class InjectPosF (n :: Nat) (x :: (Type -> Type) -> Type) (xs :: [(Type -> Type) -> Type]) | n xs -> x where

Given a type-level natural that designates a position of injection into a VariantF, return a function that performs this injection. For example, S Z which corresponds to 1 or the second position in the type-level list the variant holds, can give the injection b f -> VariantF [a, b, c] f. The injection can as well be constructed without providing the position, but it helps in case x is not unique in xs.

Methods

injectPosF :: SNat n -> x f -> VariantF xs f

Instances

InjectPosF Z x (x ': xs)

Defined in Options.Harg.Het.Variant

Methods

injectPosF :: SNat Z -> x f -> VariantF (x ': xs) f

InjectPosF n x xs => InjectPosF (S n) x (y ': xs)

Defined in Options.Harg.Het.Variant

Methods

injectPosF :: SNat (S n) -> x f -> VariantF (y ': xs) f