module splitting

[hs-rrdtool.git] / Data / HList / Prelude.hs

diff --git a/Data/HList/Prelude.hs b/Data/HList/Prelude.hs
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+module Data.HList.Prelude
+    ( HList
+    , HNil(..)
+    , hNil
+    , (:*:)(..)
+    , (.*.)
+
+    , HExtendable(..)
+    , HAppendable(..)
+
+    , Applyable(..)
+    , Applyable2(..)
+
+    , Id(..)
+    , ApplyHAppend(..)
+
+    , HFoldrable(..)
+    , HConcatable(..)
+    , HMappable(..)
+    )
+    where
+
+import Data.Typeable
+
+
+-- HList
+class HList l
+
+-- HNil
+data HNil
+    = HNil
+      deriving (Show, Eq, Ord, Read, Typeable)
+
+instance HList HNil
+
+hNil :: HNil
+hNil = HNil
+
+-- :*:
+infixr 2 :*:
+infixr 2 .*.
+
+data e :*: l
+    = e :*: l
+      deriving (Show, Eq, Ord, Read, Typeable)
+
+instance HList l => HList (e :*: l)
+
+(.*.) :: HList l => e -> l -> e :*: l
+(.*.) = (:*:)
+
+-- HExtendable
+class HExtendable e l where
+    type HExtend e l
+    hExtend :: e -> l -> HExtend e l
+
+instance HExtendable e HNil where
+    type HExtend e HNil = e :*: HNil
+    hExtend e nil = e .*. nil
+
+instance HList l => HExtendable e (e' :*: l) where
+    type HExtend e (e' :*: l) = e :*: e' :*: l
+    hExtend e (e' :*: l) = e .*. e' .*. l
+
+-- HAppendable
+infixr 1 :++:
+infixr 1 .++.
+
+class HAppendable l l' where
+    type l :++: l'
+    (.++.) :: l -> l' -> l :++: l'
+
+instance HList l => HAppendable HNil l where
+    type HNil :++: l = l
+    _ .++. l = l
+
+instance ( HAppendable l l'
+         , HList (l :++: l')
+         ) => HAppendable (e :*: l) l' where
+    type (e :*: l) :++: l' = e :*: (l :++: l')
+    (e :*: l) .++. l' = e .*. (l .++. l')
+
+-- Applyable
+class Applyable f a where
+    type Apply f a
+    apply :: f -> a -> Apply f a
+
+-- Applyable2
+class Applyable2 f a b where
+    type Apply2 f a b
+    apply2 :: f -> a -> b -> Apply2 f a b
+
+-- Id
+data Id = Id
+
+instance Applyable Id a where
+    type Apply Id a = a
+    apply _ a = a
+
+-- ApplyHAppend
+data ApplyHAppend = ApplyHAppend
+
+instance HAppendable a b => Applyable2 ApplyHAppend a b where
+    type Apply2 ApplyHAppend a b = a :++: b
+    apply2 _ a b = a .++. b
+
+-- HFoldrable
+class HFoldrable f v l where
+    type HFoldr f v l
+    hFoldr :: f -> v -> l -> HFoldr f v l
+
+instance HFoldrable 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 (e :*: l) where
+    type HFoldr f v (e :*: l) = Apply2 f e (HFoldr f v l)
+    hFoldr f v (e :*: l) = apply2 f e (hFoldr f v l)
+
+-- HConcatable
+class HConcatable 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
+
+-- HMappable
+class HMappable f l where
+    type HMap f l
+    hMap :: f -> l -> HMap f l
+
+instance HMappable f HNil where
+    type HMap f HNil = HNil
+    hMap _ _ = HNil
+
+instance ( HList (HMap f xs)
+         , Applyable f x
+         , HMappable f xs
+         ) => HMappable f (x :*: xs) where
+    type HMap f (x :*: xs) = Apply f x :*: HMap f xs
+    hMap f (x :*: xs) = apply f x .*. hMap f xs