Data.OpenWitness

Documentation

data OpenWitness :: * -> forall k. k -> *

A witness type that can witness to any type. But values cannot be constructed; they can only be generated in IO and certain other monads.

Instances

TestEquality k (OpenWitness s k)

Methods

testEquality :: f a -> f b -> Maybe ((OpenWitness s k :~: a) b)

TestHetEquality (OpenWitness s)

Methods

testHetEquality :: OpenWitness s ka a -> OpenWitness s kb b -> Maybe (HetEq kb ka a b)

Eq (OpenWitness s k a)

Methods

(==) :: OpenWitness s k a -> OpenWitness s k a -> Bool

(/=) :: OpenWitness s k a -> OpenWitness s k a -> Bool

data RealWorld

The s type for running OW in IO.

type IOWitness = OpenWitness RealWorld

An OpenWitness for IO.

newIOWitness :: forall a. IO (IOWitness a)

Generate a new IOWitness in IO.

data OW s a

A runnable monad in which OpenWitness values can be generated. The s parameter plays the same role as it does in ST, preventing OpenWitness values from one run being used in another.

Instances

Monad (OW k s)

Methods

(>>=) :: OW k s a -> (a -> OW k s b) -> OW k s b

(>>) :: OW k s a -> OW k s b -> OW k s b

return :: a -> OW k s a

fail :: String -> OW k s a

Functor (OW k s)

Methods

fmap :: (a -> b) -> OW k s a -> OW k s b

(<$) :: a -> OW k s b -> OW k s a

MonadFix (OW k s)

Methods

mfix :: (a -> OW k s a) -> OW k s a

Applicative (OW k s)

Methods

pure :: a -> OW k s a

(<*>) :: OW k s (a -> b) -> OW k s a -> OW k s b

(*>) :: OW k s a -> OW k s b -> OW k s b

(<*) :: OW k s a -> OW k s b -> OW k s a

newOpenWitnessOW :: forall s a. OW s (OpenWitness s a)

Generate a new OpenWitness in OW.

runOW :: forall a. (forall s. OW s a) -> a

Run an OW computation.

owToIO :: OW RealWorld a -> IO a

Run an OW computation in IO.

iowitness :: TypeQ -> Q Exp

Template Haskell function to declare IOWitness values.