Network.Haskoin.Util.BuildMonad

The Build type, and associated operations.

Build monad

data Build a

The Build monad represents computations that can be in one of three states:

• Complete
• Partial
• Broken

It extends the Either monad with an additional Partial value to describe a valid computation flagged with a Partial context. The Build monad is useful when you describe computations where parts of the computation are either complete, partially complete or broken. Combining only Complete computations will produce a Complete result. However, if one of the computations is Partial, the whole computation will be Partial as well. And if some computation is Broken, the whole computation will be broken as well.

The Build monad is used by Haskoin to describe the state of the transaction signing computation. To sign a transaction, all input scripts need to be signed. The whole transaction will be completely signed only if all the input scripts are completely signed. If any of the inputs is partially signed, then the whole transaction will be partially signed as well. And the whole transaction is broken if one of the inputs failed to parse or is broken.

Constructors

Complete

Describes a successful complete computation

Fields

runBuild :: a

Partial

Describes a successful but partial computation

Fields

runBuild :: a

Broken

Describes a broken computation

Fields

runBroken :: String

Instances

Monad Build

Functor Build

Eq a => Eq (Build a)

Show a => Show (Build a)

Arbitrary a => Arbitrary (Build a)

isComplete :: Build a -> Bool

Returns True if the Build value is Complete

isPartial :: Build a -> Bool

Returns True if the Build value is Partial

isBroken :: Build a -> Bool

Return True if the Build value is Broken

eitherToBuild :: Either String a -> Build a

Transforms an Either String value into a Build value. Right is mapped to Complete and Left is mapped to Broken

buildToEither :: Build a -> Either String a

Transforms a Build value into an Either String value. Complete and Partial are mapped to Right and Broken is mapped to Left.

guardPartial :: Bool -> Build ()

Binds a Partial value to the computation when the predicate is False.

BuildT transformer monad

newtype BuildT m a

BuildT transformer monad

Constructors

BuildT

Fields

runBuildT :: m (Build a)

Instances

MonadTrans BuildT

Monad m => Monad (BuildT m)

Functor m => Functor (BuildT m)

MonadIO m => MonadIO (BuildT m)

liftBuild :: Monad m => Build a -> BuildT m a

Lift a Build computation into the BuildT monad