Safe Haskell | None |
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- data Sealed a where
- seal :: a wX -> Sealed a
- data Sealed2 a where
- seal2 :: a wX wY -> Sealed2 a
- data FlippedSeal a wY where
- 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 {
- unPoly :: forall wX. a wX

- newtype Stepped f a wX = Stepped {
- unStepped :: f (a wX)

- newtype FreeLeft p = FLInternal (Poly (Stepped Sealed p))
- newtype FreeRight p = FRInternal (Poly (FlippedSeal p))
- unFreeLeft :: FreeLeft p -> Sealed (p wX)
- unFreeRight :: FreeRight p -> FlippedSeal p wX
- class Gap w where

# 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.

data FlippedSeal a wY where

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

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

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

newtype Poly a

newtype Stepped 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.

FLInternal (Poly (Stepped Sealed p)) |

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.

FRInternal (Poly (FlippedSeal p)) |

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

Unwrap a `FreeLeft`

value

unFreeRight :: FreeRight p -> FlippedSeal p wX

Unwrap a `FreeRight`

value

class Gap w where

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 (:>:)'