darcs-2.11.0: a distributed, interactive, smart revision control system

Safe HaskellNone

Darcs.Patch.Witnesses.Sealed

Synopsis

Documentation

data Sealed a where

A Sealed type is a way of hide an existentially quantified type parameter, in this case wX, inside the type. Note that the only thing we can currently recover about the existentially quantified type wX is that it exists.

Constructors

Sealed :: a wX -> Sealed a 

Instances

MyEq a => Eq (Sealed (a wX)) 
Show1 a => Show (Sealed a) 

seal :: a wX -> Sealed a

data Sealed2 a where

The same as Sealed but for two parameters (wX and wY).

Constructors

Sealed2 :: !(a wX wY) -> Sealed2 a 

Instances

Show2 a => Show (Sealed2 a) 

seal2 :: a wX wY -> Sealed2 a

data FlippedSeal a wY where

Constructors

FlippedSeal :: !(a wX wY) -> FlippedSeal a wY 

flipSeal :: a wX wY -> FlippedSeal a wY

unsafeUnseal :: Sealed a -> a wX

unsafeUnsealFlipped :: FlippedSeal a wY -> a wX wY

unsafeUnseal2 :: Sealed2 a -> a wX wY

unseal :: (forall wX. a wX -> b) -> Sealed a -> b

unsealM :: Monad m => m (Sealed a) -> (forall wX. a wX -> m b) -> m b

liftSM :: Monad m => (forall wX. a wX -> b) -> m (Sealed a) -> m b

mapSeal :: (forall wX. a wX -> b wX) -> Sealed a -> Sealed b

mapFlipped :: (forall wX. a wX wY -> b wX wZ) -> FlippedSeal a wY -> FlippedSeal b wZ

unseal2 :: (forall wX wY. a wX wY -> b) -> Sealed2 a -> b

mapSeal2 :: (forall wX wY. a wX wY -> b wX wY) -> Sealed2 a -> Sealed2 b

unsealFlipped :: (forall wX wY. a wX wY -> b) -> FlippedSeal a wZ -> b

newtype Poly a

Poly is similar to Sealed, but the type argument is universally quantified instead of being existentially quantified.

Constructors

Poly 

Fields

unPoly :: forall wX. a wX
 

newtype Stepped f a wX

Stepped is a type level composition operator. For example, Stepped (Sealed p) is equivalent to \x -> Sealed (p x)

Constructors

Stepped 

Fields

unStepped :: f (a wX)
 

newtype FreeLeft p

FreeLeft p is forall x . exists y . p x y In other words the caller is free to specify the left witness, and then the right witness is an existential. Note that the order of the type constructors is important for ensuring that y is dependent on the x that is supplied. This is why Stepped is needed, rather than writing the more obvious Sealed (Poly p) which would notionally have the same quantification of the type witnesses.

Constructors

FLInternal (Poly (Stepped Sealed p)) 

Instances

newtype FreeRight p

FreeLeft p is forall y . exists x . p x y In other words the caller is free to specify the right witness, and then the left witness is an existential. Note that the order of the type constructors is important for ensuring that x is dependent on the y that is supplied.

Constructors

FRInternal (Poly (FlippedSeal p)) 

Instances

unFreeLeft :: FreeLeft p -> Sealed (p wX)

Unwrap a FreeLeft value

unFreeRight :: FreeRight p -> FlippedSeal p wX

Unwrap a FreeRight value

class Gap w where

Gap abstracts over FreeLeft and FreeRight for code constructing these values

Methods

emptyGap :: (forall wX. p wX wX) -> w p

An empty Gap, e.g. NilFL or NilRL

freeGap :: (forall wX wY. p wX wY) -> w p

A Gap constructed from a completely polymorphic value, for example the constructors for primitive patches

joinGap :: (forall wX wY wZ. p wX wY -> q wY wZ -> r wX wZ) -> w p -> w q -> w r

Compose two Gap values together in series, e.g. 'joinGap (+>+)' or 'joinGap (:>:)'