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servant: clean up some white spaces, add link explaining why Or works.

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This commit is contained in:
Christian Marie 2015-05-14 00:07:57 +10:00
parent c87b846815
commit 13fcb4f3f1
1 changed files with 25 additions and 22 deletions
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servant/src/Servant/Utils/Links.hs
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@ -137,16 +137,19 @@ data Link = Link
} deriving Show } deriving Show
-- | If either a or b produce an empty constraint, produce an empty constraint. -- | If either a or b produce an empty constraint, produce an empty constraint.
--
-- This works because of:
-- https://ghc.haskell.org/trac/ghc/wiki/NewAxioms/CoincidentOverlap
type family Or (a :: Constraint) (b :: Constraint) :: Constraint where type family Or (a :: Constraint) (b :: Constraint) :: Constraint where
Or () b = () Or () b = ()
Or a () = () Or a () = ()
-- | If both a or b produce an empty constraint, produce an empty constraint. -- | If both a or b produce an empty constraint, produce an empty constraint.
type family And (a :: Constraint) (b :: Constraint) :: Constraint where type family And (a :: Constraint) (b :: Constraint) :: Constraint where
And () () = () And () () = ()
-- | You may use this type family to tell the type checker that your custom type -- | You may use this type family to tell the type checker that your custom
-- may be skipped as part of a link. This is useful for things like -- type may be skipped as part of a link. This is useful for things like
-- 'QueryParam' that are optional in a URI and do not affect them if they are -- 'QueryParam' that are optional in a URI and do not affect them if they are
-- omitted. -- omitted.
-- --
@ -162,30 +165,30 @@ type family IsElem' a s :: Constraint
-- | Closed type family, check if endpoint is within api -- | Closed type family, check if endpoint is within api
type family IsElem endpoint api :: Constraint where type family IsElem endpoint api :: Constraint where
IsElem e (sa :<|> sb) = Or (IsElem e sa) (IsElem e sb) IsElem e (sa :<|> sb) = Or (IsElem e sa) (IsElem e sb)
IsElem (e :> sa) (e :> sb) = IsElem sa sb IsElem (e :> sa) (e :> sb) = IsElem sa sb
IsElem sa (Header x :> sb) = IsElem sa sb IsElem sa (Header x :> sb) = IsElem sa sb
IsElem sa (ReqBody y x :> sb) = IsElem sa sb IsElem sa (ReqBody y x :> sb) = IsElem sa sb
IsElem (e :> sa) (Capture x y :> sb) = IsElem sa sb IsElem (e :> sa) (Capture x y :> sb) = IsElem sa sb
IsElem sa (QueryParam x y :> sb) = IsElem sa sb IsElem sa (QueryParam x y :> sb) = IsElem sa sb
IsElem sa (QueryParams x y :> sb) = IsElem sa sb IsElem sa (QueryParams x y :> sb) = IsElem sa sb
IsElem sa (QueryFlag x :> sb) = IsElem sa sb IsElem sa (QueryFlag x :> sb) = IsElem sa sb
IsElem sa (MatrixParam x y :> sb) = IsElem sa sb IsElem sa (MatrixParam x y :> sb) = IsElem sa sb
IsElem sa (MatrixParams x y :> sb) = IsElem sa sb IsElem sa (MatrixParams x y :> sb) = IsElem sa sb
IsElem sa (MatrixFlag x :> sb) = IsElem sa sb IsElem sa (MatrixFlag x :> sb) = IsElem sa sb
IsElem (Get ct typ) (Get ct' typ) = IsSubList ct ct' IsElem (Get ct typ) (Get ct' typ) = IsSubList ct ct'
IsElem (Post ct typ) (Post ct' typ) = IsSubList ct ct' IsElem (Post ct typ) (Post ct' typ) = IsSubList ct ct'
IsElem (Put ct typ) (Put ct' typ) = IsSubList ct ct' IsElem (Put ct typ) (Put ct' typ) = IsSubList ct ct'
IsElem (Delete ct typ) (Delete ct' typ) = IsSubList ct ct' IsElem (Delete ct typ) (Delete ct' typ) = IsSubList ct ct'
IsElem e e = () IsElem e e = ()
IsElem e a = IsElem' e a IsElem e a = IsElem' e a
type family IsSubList a b :: Constraint where type family IsSubList a b :: Constraint where
IsSubList '[] b = () IsSubList '[] b = ()
IsSubList '[x] (x ': xs) = () IsSubList '[x] (x ': xs) = ()
IsSubList '[x] (y ': ys) = IsSubList '[x] ys IsSubList '[x] (y ': ys) = IsSubList '[x] ys
IsSubList (x ': xs) y = IsSubList '[x] y `And` IsSubList xs y IsSubList (x ': xs) y = IsSubList '[x] y `And` IsSubList xs y
-- Phantom types for Param -- Phantom types for Param
data Matrix data Matrix