-{-# LANGUAGE DeriveDataTypeable,
- FlexibleContexts,
- FlexibleInstances,
- MultiParamTypeClasses,
- TypeFamilies,
- TypeOperators,
- UndecidableInstances
+{- -*- coding: utf-8 -*- -}
+{-# LANGUAGE
+ DeriveDataTypeable,
+ EmptyDataDecls,
+ FlexibleContexts,
+ FlexibleInstances,
+ FunctionalDependencies,
+ MultiParamTypeClasses,
+ OverlappingInstances,
+ TypeFamilies,
+ TypeOperators,
+ UndecidableInstances
#-}
module Data.HList.Prelude
( HList
, HCons(..)
, hCons
- , HExtendable(..)
- , HAppendable(..)
+ , HExtendT(..)
+ , HAppendT(..)
- , Applyable(..)
- , Applyable2(..)
+ , ApplyT(..)
+ , Apply2T(..)
, Id(..)
- , ApplyHAppend(..)
-
- , HFoldrable(..)
- , HConcatable(..)
- , HMappable(..)
+ , HAppendA(..)
+
+ , HFoldrT(..)
+ , HConcatT(..)
+ , HMapT(..)
+
+ , HAll
+ , HLength
+
+ , Fail
+ , TypeFound
+ , TypeNotFound
+ , HOccursMany(..)
+ , HOccursMany1(..)
+ , HOccursOpt(..)
+ , HOccurs(..)
+ , HOccursNot(..)
)
where
import Data.Typeable
+import Types.Data.Bool
+import Types.Data.Num hiding ((:*:))
-- HList
hCons :: HList l => e -> l -> HCons e l
hCons = HCons
--- HExtendable
-infixr 2 :*:
-infixr 2 .*.
+-- HExtendT
+infixr 2 :&:
+infixr 2 .&.
-class HExtendable e l where
- type e :*: l
- (.*.) :: e -> l -> e :*: l
+class HExtendT e l where
+ type e :&: l
+ (.&.) :: e -> l -> e :&: l
-instance HExtendable e HNil where
- type e :*: HNil = HCons e HNil
- e .*. nil = hCons e nil
+instance HExtendT e HNil where
+ type e :&: HNil = HCons e HNil
+ e .&. nil = hCons e nil
-instance HList l => HExtendable e (HCons e' l) where
- type e :*: HCons e' l = HCons e (HCons e' l)
- e .*. HCons e' l = hCons e (hCons e' l)
+instance HList l => HExtendT e (HCons e' l) where
+ type e :&: HCons e' l = HCons e (HCons e' l)
+ e .&. HCons e' l = hCons e (hCons e' l)
--- HAppendable
+-- HAppendT
infixr 1 :++:
infixr 1 .++.
-class HAppendable l l' where
+class HAppendT l l' where
type l :++: l'
(.++.) :: l -> l' -> l :++: l'
-instance HList l => HAppendable HNil l where
+instance HList l => HAppendT HNil l where
type HNil :++: l = l
_ .++. l = l
instance ( HList (l :++: l')
- , HAppendable l l'
- ) => HAppendable (HCons e l) l' where
+ , HAppendT l l'
+ ) => HAppendT (HCons e l) l' where
type HCons e l :++: l' = HCons e (l :++: l')
(HCons e l) .++. l' = hCons e (l .++. l')
--- Applyable
-class Applyable f a where
+-- ApplyT
+class ApplyT f a where
type Apply f a
apply :: f -> a -> Apply f a
+ apply _ _ = undefined
--- Applyable2
-class Applyable2 f a b where
+-- Apply2T
+class Apply2T f a b where
type Apply2 f a b
apply2 :: f -> a -> b -> Apply2 f a b
+ apply2 _ _ _ = undefined
-- Id
data Id = Id
-instance Applyable Id a where
+instance ApplyT Id a where
type Apply Id a = a
apply _ a = a
--- ApplyHAppend
-data ApplyHAppend = ApplyHAppend
+-- HAppendA
+data HAppendA = HAppendA
-instance HAppendable a b => Applyable2 ApplyHAppend a b where
- type Apply2 ApplyHAppend a b = a :++: b
+instance HAppendT a b => Apply2T HAppendA a b where
+ type Apply2 HAppendA a b = a :++: b
apply2 _ a b = a .++. b
--- HFoldrable
-class HFoldrable f v l where
+-- HFoldrT
+class HFoldrT f v l where
type HFoldr f v l
hFoldr :: f -> v -> l -> HFoldr f v l
-instance HFoldrable f v HNil where
+instance HFoldrT f v HNil where
type HFoldr f v HNil = v
hFoldr _ v _ = v
-instance ( HFoldrable f v l
- , Applyable2 f e (HFoldr f v l)
- ) => HFoldrable f v (HCons e l) where
+instance ( HFoldrT f v l
+ , Apply2T f e (HFoldr f v l)
+ ) => HFoldrT f v (HCons e l) where
type HFoldr f v (HCons e l) = Apply2 f e (HFoldr f v l)
hFoldr f v (HCons e l) = apply2 f e (hFoldr f v l)
--- HConcatable
-class HConcatable ls where
+-- HConcatT
+class HConcatT ls where
type HConcat ls
hConcat :: ls -> HConcat ls
-instance HFoldrable ApplyHAppend HNil ls => HConcatable ls where
- type HConcat ls = HFoldr ApplyHAppend HNil ls
- hConcat ls = hFoldr ApplyHAppend hNil ls
+instance HFoldrT HAppendA HNil ls => HConcatT ls where
+ type HConcat ls = HFoldr HAppendA HNil ls
+ hConcat ls = hFoldr HAppendA hNil ls
--- HMappable
-class HMappable f l where
+-- HMapT
+class HMapT f l where
type HMap f l
hMap :: f -> l -> HMap f l
-instance HMappable f HNil where
+instance HMapT f HNil where
type HMap f HNil = HNil
hMap _ _ = hNil
-instance ( Applyable f x
- , HMappable f xs
+instance ( ApplyT f x
+ , HMapT f xs
, HList (HMap f xs)
- ) => HMappable f (HCons x xs) where
+ ) => HMapT f (HCons x xs) where
type HMap f (HCons x xs) = HCons (Apply f x) (HMap f xs)
hMap f (HCons x xs) = hCons (apply f x) (hMap f xs)
+
+-- HAll
+type family HAll f l
+type instance HAll f HNil = True
+type instance HAll f (HCons x xs) = If (Apply f x) (HAll f xs) False
+
+-- HLength
+type family HLength l
+type instance HLength HNil = D0
+type instance HLength (HCons e l) = Succ (HLength l)
+
+-- Fail
+class Fail a
+
+-- HOccursMany (zero or more)
+class HOccursMany e l where
+ hOccursMany :: l -> [e]
+
+instance HOccursMany e HNil where
+ hOccursMany _ = []
+
+instance ( HList l
+ , HOccursMany e l
+ )
+ => HOccursMany e (HCons e l)
+ where
+ hOccursMany (HCons e l) = e : hOccursMany l
+
+instance ( HList l
+ , HOccursMany e l
+ )
+ => HOccursMany e (HCons e' l)
+ where
+ hOccursMany (HCons _ l) = hOccursMany l
+
+-- HOccursMany1 (one or more)
+class HOccursMany1 e l where
+ hOccursMany1 :: l -> [e]
+
+instance Fail (TypeNotFound e) => HOccursMany1 e HNil where
+ hOccursMany1 _ = undefined
+
+instance ( HList l
+ , HOccursMany e l
+ )
+ => HOccursMany1 e (HCons e l)
+ where
+ hOccursMany1 (HCons e l) = e : hOccursMany l
+
+instance ( HList l
+ , HOccursMany1 e l
+ )
+ => HOccursMany1 e (HCons e' l)
+ where
+ hOccursMany1 (HCons _ l) = hOccursMany1 l
+
+-- HOccursOpt (zero or one)
+class HOccursOpt e l where
+ hOccursOpt :: l -> Maybe e
+
+instance HOccursOpt e HNil where
+ hOccursOpt _ = Nothing
+
+instance HOccursNot e l => HOccursOpt e (HCons e l) where
+ hOccursOpt (HCons e _) = Just e
+
+instance HOccursOpt e l => HOccursOpt e (HCons e' l) where
+ hOccursOpt (HCons _ l) = hOccursOpt l
+
+-- HOccurs (one)
+class HOccurs e l where
+ hOccurs :: l -> e
+
+data TypeNotFound e
+
+instance Fail (TypeNotFound e) => HOccurs e HNil
+ where
+ hOccurs = undefined
+
+instance ( HList l
+ , HOccursNot e l
+ )
+ => HOccurs e (HCons e l)
+ where
+ hOccurs (HCons e _) = e
+
+instance ( HList l
+ , HOccurs e l
+ )
+ => HOccurs e (HCons e' l)
+ where
+ hOccurs (HCons _ l) = hOccurs l
+
+-- HOccursNot (zero)
+data TypeFound e
+class HOccursNot e l
+instance HOccursNot e HNil
+instance Fail (TypeFound e) => HOccursNot e (HCons e l)
+instance HOccursNot e l => HOccursNot e (HCons e' l)
+
+{-
+{-
+"Strongly Typed Heterogeneous Collections"
+ — August 26, 2004
+ Oleg Kiselyov
+ Ralf Lämmel
+ Keean Schupke
+==========================
+9 By chance or by design?
+
+We will now discuss the issues surrounding the definition of type
+equality, inequality, and unification — and give implementations
+differing in simplicity, genericity, and portability.
+
+We define the class TypeEq x y b for type equality. The class relates
+two types x and y to the type HTrue in case the two types are equal;
+otherwise, the types are related to HFalse. We should point out
+however groundness issues. If TypeEq is to return HTrue, the types
+must be ground; TypeEq can return HFalse even for unground types,
+provided they are instantiated enough to determine that they are not
+equal. So, TypeEq is total for ground types, and partial for unground
+types. We also define the class TypeCast x y: a constraint that holds
+only if the two types x and y are unifiable. Regarding groundness of x
+and y, the class TypeCast is less restricted than TypeEq. That is,
+TypeCast x y succeeds even for unground types x and y in case they can
+be made equal through unification. TypeEq and TypeCast are related to
+each other as fol- lows. Whenever TypeEq succeeds with HTrue, TypeCast
+succeeds as well. Whenever TypeEq succeeds with HFalse, TypeCast
+fails. But for unground types, when TypeCast succeeds, TypeEq might
+fail. So the two complement each other for unground types. Also,
+TypeEq is a partial predicate, while TypeCast is a relation. That’s
+why both are useful.
+ -}
+class TypeEq x y b | x y -> b
+instance TypeEq x x True
+instance TypeCast False b =>
+ TypeEq x y b
+
+class TypeCast a b | a -> b, b -> a
+ where
+ typeCast :: a -> b
+
+class TypeCast' t a b | t a -> b, t b -> a
+ where
+ typeCast' :: t -> a -> b
+
+class TypeCast'' t a b | t a -> b, t b -> a
+ where
+ typeCast'' :: t -> a -> b
+
+instance TypeCast' () a b => TypeCast a b
+ where
+ typeCast x = typeCast' () x
+
+instance TypeCast'' t a b => TypeCast' t a b
+ where
+ typeCast' = typeCast''
+
+instance TypeCast'' () a a
+ where
+ typeCast'' _ x = x
+-}
\ No newline at end of file
projects / hs-rrdtool.git / blobdiff