Strongweak.Chain

Documentation

newtype SWChain (n :: Natural) a

When weakening (or strengthening), chain the operation n times.

You may achieve this without extra newtypes by nesting uses of SW. However, strongweak generics can't handle this, forcing you to write manual instances.

SWChain provides this nesting behaviour in a type. In return for adding a boring newtype layer to the strong representation, you can chain weakening and strengthenings without having to write them manually.

The type works as follows:

Weakened (SWChain 0 a) = a
Weakened (SWChain 1 a) = Weakened a
Weakened (SWChain 2 a) = Weakened (Weakened a)
Weakened (SWChain n a) = WeakenedN n a

And so on. (This type is only much use from n = 2 onwards.)

You may also use this as a "via" type:

newtype A (s :: Strength) = A { a1 :: SW s (Identity (SW s Word8)) }
deriving via SWChain 2 (Identity Word8) instance     Weaken (A Strong)
deriving via SWChain 2 (Identity Word8) instance Strengthen (A Strong)

Constructors

SWChain

Fields

• unSWChain :: a

Instances

Show a => Show (SWChain n a)

Defined in Strongweak.Chain

Methods

showsPrec :: Int -> SWChain n a -> ShowS

show :: SWChain n a -> String

showList :: [SWChain n a] -> ShowS

Eq a => Eq (SWChain n a)

Defined in Strongweak.Chain

Methods

(==) :: SWChain n a -> SWChain n a -> Bool

(/=) :: SWChain n a -> SWChain n a -> Bool

Ord a => Ord (SWChain n a)

Defined in Strongweak.Chain

Methods

compare :: SWChain n a -> SWChain n a -> Ordering

(<) :: SWChain n a -> SWChain n a -> Bool

(<=) :: SWChain n a -> SWChain n a -> Bool

(>) :: SWChain n a -> SWChain n a -> Bool

(>=) :: SWChain n a -> SWChain n a -> Bool

max :: SWChain n a -> SWChain n a -> SWChain n a

min :: SWChain n a -> SWChain n a -> SWChain n a

StrengthenN n a => Strengthen (SWChain n a)

Defined in Strongweak.Chain

Methods

strengthen :: Weakened (SWChain n a) -> Either StrengthenFailure' (SWChain n a)

WeakenN n a => Weaken (SWChain n a)

Defined in Strongweak.Chain

Associated Types

type Weakened (SWChain n a)

Defined in Strongweak.Chain

type Weakened (SWChain n a) = WeakenedN n a

Methods

weaken :: SWChain n a -> Weakened (SWChain n a)

type Weakened (SWChain n a)

Defined in Strongweak.Chain

type Weakened (SWChain n a) = WeakenedN n a

strengthenN :: StrengthenN n a => WeakenedN n a -> Either StrengthenFailure' a