Data.Promotion.Prelude.Maybe

Defines promoted functions and datatypes relating to Maybe, including a promoted version of all the definitions in Data.Maybe.

Because many of these definitions are produced by Template Haskell, it is not possible to create proper Haddock documentation. Please look up the corresponding operation in Data.Maybe. Also, please excuse the apparent repeated variable names. This is due to an interaction between Template Haskell and Haddock.

Promoted functions from Data.Maybe

maybe_ :: forall b a. b -> (a -> b) -> Maybe a -> b

type family Maybe_ a a a :: b

Equations

Maybe_ n z Nothing = n

Maybe_ z f (Just x) = Apply f x

The preceding two definitions is derived from the function maybe in Data.Maybe. The extra underscore is to avoid name clashes with the type Maybe.

type family IsJust a :: Bool

Equations

IsJust Nothing = FalseSym0

IsJust (Just z) = TrueSym0

type family IsNothing a :: Bool

Equations

IsNothing Nothing = TrueSym0

IsNothing (Just z) = FalseSym0

type family FromJust a :: a

Equations

FromJust Nothing = Apply ErrorSym0 "Maybe.fromJust: Nothing"

FromJust (Just x) = x

type family FromMaybe a a :: a

Equations

FromMaybe d x = Case_1627754863 d x (Let_1627754854Scrutinee_1627754775Sym2 d x)

type family MaybeToList a :: [a]

Equations

MaybeToList Nothing = `[]`

MaybeToList (Just x) = Apply (Apply (:$) x) `[]`

type family ListToMaybe a :: Maybe a

Equations

ListToMaybe `[]` = NothingSym0

ListToMaybe ((:) a z) = Apply JustSym0 a

type family CatMaybes a :: [a]

Equations

CatMaybes `[]` = `[]`

CatMaybes ((:) (Just x) xs) = Apply (Apply (:$) x) (Apply CatMaybesSym0 xs)

CatMaybes ((:) Nothing xs) = Apply CatMaybesSym0 xs

type family MapMaybe a a :: [b]

Equations

MapMaybe z `[]` = `[]`

MapMaybe f ((:) x xs) = Case_1627754820 f x xs (Let_1627754806Scrutinee_1627754777Sym3 f x xs)

Defunctionalization symbols

type NothingSym0 = Nothing

data JustSym0 l

Instances

SuppressUnusedWarnings (TyFun k (Maybe k) -> *) (JustSym0 k)

type Apply (Maybe k) k (JustSym0 k) l0 = JustSym1 k l0

type JustSym1 t = Just t

data Maybe_Sym0 l

Instances

SuppressUnusedWarnings (TyFun k (TyFun (TyFun k k -> *) (TyFun (Maybe k) k -> *) -> *) -> *) (Maybe_Sym0 k k)

type Apply (TyFun (TyFun k1 k -> *) (TyFun (Maybe k1) k -> *) -> *) k (Maybe_Sym0 k k1) l0 = Maybe_Sym1 k k1 l0

data Maybe_Sym1 l l

Instances

SuppressUnusedWarnings (k -> TyFun (TyFun k k -> *) (TyFun (Maybe k) k -> *) -> *) (Maybe_Sym1 k k)

type Apply (TyFun (Maybe k) k1 -> *) (TyFun k k1 -> *) (Maybe_Sym1 k1 k l1) l0 = Maybe_Sym2 k1 k l1 l0

data Maybe_Sym2 l l l

Instances

SuppressUnusedWarnings (k -> (TyFun k k -> *) -> TyFun (Maybe k) k -> *) (Maybe_Sym2 k k)

type Apply k (Maybe k1) (Maybe_Sym2 k k1 l1 l2) l0 = Maybe_Sym3 k k1 l1 l2 l0

type Maybe_Sym3 t t t = Maybe_ t t t

data IsJustSym0 l

Instances

SuppressUnusedWarnings (TyFun (Maybe k) Bool -> *) (IsJustSym0 k)

type Apply Bool (Maybe k) (IsJustSym0 k) l0 = IsJustSym1 k l0

type IsJustSym1 t = IsJust t

data IsNothingSym0 l

Instances

SuppressUnusedWarnings (TyFun (Maybe k) Bool -> *) (IsNothingSym0 k)

type Apply Bool (Maybe k) (IsNothingSym0 k) l0 = IsNothingSym1 k l0

type IsNothingSym1 t = IsNothing t

data FromJustSym0 l

Instances

SuppressUnusedWarnings (TyFun (Maybe k) k -> *) (FromJustSym0 k)

type Apply k (Maybe k) (FromJustSym0 k) l0 = FromJustSym1 k l0

type FromJustSym1 t = FromJust t

data FromMaybeSym0 l

Instances

SuppressUnusedWarnings (TyFun k (TyFun (Maybe k) k -> *) -> *) (FromMaybeSym0 k)

type Apply (TyFun (Maybe k) k -> *) k (FromMaybeSym0 k) l0 = FromMaybeSym1 k l0

data FromMaybeSym1 l l

Instances

SuppressUnusedWarnings (k -> TyFun (Maybe k) k -> *) (FromMaybeSym1 k)

type Apply k (Maybe k) (FromMaybeSym1 k l1) l0 = FromMaybeSym2 k l1 l0

type FromMaybeSym2 t t = FromMaybe t t

data MaybeToListSym0 l

Instances

SuppressUnusedWarnings (TyFun (Maybe k) [k] -> *) (MaybeToListSym0 k)

type Apply [k] (Maybe k) (MaybeToListSym0 k) l0 = MaybeToListSym1 k l0

type MaybeToListSym1 t = MaybeToList t

data ListToMaybeSym0 l

Instances

SuppressUnusedWarnings (TyFun [k] (Maybe k) -> *) (ListToMaybeSym0 k)

type Apply (Maybe k) [k] (ListToMaybeSym0 k) l0 = ListToMaybeSym1 k l0

type ListToMaybeSym1 t = ListToMaybe t

data CatMaybesSym0 l

Instances

SuppressUnusedWarnings (TyFun [Maybe k] [k] -> *) (CatMaybesSym0 k)

type Apply [k] [Maybe k] (CatMaybesSym0 k) l0 = CatMaybesSym1 k l0

type CatMaybesSym1 t = CatMaybes t

data MapMaybeSym0 l

Instances

SuppressUnusedWarnings (TyFun (TyFun k (Maybe k) -> *) (TyFun [k] [k] -> *) -> *) (MapMaybeSym0 k k)

type Apply (TyFun [k] [k1] -> *) (TyFun k (Maybe k1) -> *) (MapMaybeSym0 k k1) l0 = MapMaybeSym1 k k1 l0

data MapMaybeSym1 l l

Instances

SuppressUnusedWarnings ((TyFun k (Maybe k) -> *) -> TyFun [k] [k] -> *) (MapMaybeSym1 k k)

type Apply [k1] [k] (MapMaybeSym1 k k1 l1) l0 = MapMaybeSym2 k k1 l1 l0

type MapMaybeSym2 t t = MapMaybe t t