| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Darcs.Patch.Witnesses.Sealed
Synopsis
- 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
- unseal :: (forall wX. a wX -> b) -> Sealed a -> 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
- data Dup p wX wY where
- data FreeLeft p
- data FreeRight p
- unFreeLeft :: FreeLeft p -> Sealed (p wX)
- unFreeRight :: FreeRight p -> FlippedSeal p wX
- class Gap w where
Documentation
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.
The same as Sealed but for two parameters (wX and wY).
data FlippedSeal a wY where Source #
Constructors
| FlippedSeal :: !(a wX wY) -> FlippedSeal a wY |
flipSeal :: a wX wY -> FlippedSeal a wY Source #
mapFlipped :: (forall wX. a wX wY -> b wX wZ) -> FlippedSeal a wY -> FlippedSeal b wZ Source #
unsealFlipped :: (forall wX wY. a wX wY -> b) -> FlippedSeal a wZ -> b Source #
data Dup p wX wY where Source #
Duplicate a single witness. This is for situations where a patch-like type is expected, i.e. a type with two witnesses, but we have only a type with one witness. Naturally, any concrete value must have both witnesses agreeing.
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.
Instances
FreeRight 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.
Instances
unFreeRight :: FreeRight p -> FlippedSeal p wX Source #
Unwrap a FreeRight value
Methods
emptyGap :: (forall wX. p wX wX) -> w p Source #
An empty Gap, e.g. NilFL or NilRL
freeGap :: (forall wX wY. p wX wY) -> w p Source #
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 Source #
Compose two Gap values together in series, e.g. 'joinGap (+>+)' or 'joinGap (:>:)'