Safe Haskell | None |
---|---|
Language | Haskell98 |
Cardano.Ledger.Era
Description
Support for multiple (Shelley-based) eras in the ledger.
Synopsis
- class (Crypto (Crypto e), Typeable e) => Era e
- type family Crypto e :: Type
- type family PreviousEra era :: Type
- type family TranslationContext era :: Type
- class (Era era, Era (PreviousEra era)) => TranslateEra era f where
- type TranslationError era f :: Type
- translateEra :: TranslationContext era -> f (PreviousEra era) -> Except (TranslationError era f) (f era)
- translateEra' :: (TranslateEra era f, TranslationError era f ~ Void) => TranslationContext era -> f (PreviousEra era) -> f era
- translateEraMaybe :: (TranslateEra era f, TranslationError era f ~ ()) => TranslationContext era -> f (PreviousEra era) -> Maybe (f era)
Documentation
class (Crypto (Crypto e), Typeable e) => Era e Source #
Instances
Crypto c => Era (ShelleyEra c) Source # | |
Defined in Cardano.Ledger.Shelley Associated Types type Crypto (ShelleyEra c) Source # |
type family Crypto e :: Type Source #
Instances
type Crypto (ShelleyEra c) Source # | |
Defined in Cardano.Ledger.Shelley |
type family PreviousEra era :: Type Source #
Map an era to its predecessor.
For example:
type instance PreviousEra (AllegraEra c) = ShelleyEra c
type family TranslationContext era :: Type Source #
Per-era context used for TranslateEra
.
This context will be passed to the translation instances of all types of that particular era. In practice, most instances won't need the context, but this approach makes the translation composable (as opposed to having a separate context per type).
class (Era era, Era (PreviousEra era)) => TranslateEra era f where Source #
Translation of types between eras, e.g., from Shelley to Allegra.
When era
is just a phantom type parameter, an empty standalone deriving can be used:
newtype Foo era = Foo Int instance TranslateEra (Allegra c) Foo
Note that one could use DerivingAnyClass
(deriving (TranslateEra (Allegra
c))
), but this would introduce an undesired coupling between the
era-parametric type and (a) particular era(s). The intention is to have a
module with orphan instances per era.
In most cases, the era
parameter won't be phantom, and a manual instance
will have to be written:
newtype Bar era = Bar (TxBody era) instance CryptoClass.Crypto c => TranslateEra (Allegra c) Bar where translateEra ctxt = Bar <$> translateEra ctxt -- With the following instance being in scope: instance CryptoClass.Crypto c => TranslatEra (Allegra c) TxBody
Note: we use PreviousEra
instead of NextEra
as an era definitely knows
its predecessor, but not necessarily its successor. Moreover, one could argue
that it makes more sense to define the translation from era A to era B where
era B is defined, than where era A is defined.
Minimal complete definition
Nothing
Associated Types
type TranslationError era f :: Type Source #
Most translations should be infallible (default instance), but we leave the door open for partial translations.
For a partial translation, override the default type to be ()
or a
concrete error type.
type TranslationError era f = Void
Methods
translateEra :: TranslationContext era -> f (PreviousEra era) -> Except (TranslationError era f) (f era) Source #
Translate a type f
parameterised by the era from an era to the era
after it.
The translation is a given the translation context of era
.
A default instance is provided for when the two types are Coercible
.
default translateEra :: Coercible (f (PreviousEra era)) (f era) => TranslationContext era -> f (PreviousEra era) -> Except (TranslationError era f) (f era) Source #
translateEra' :: (TranslateEra era f, TranslationError era f ~ Void) => TranslationContext era -> f (PreviousEra era) -> f era Source #
Variant of translateEra
for when TranslationError
is Void
and the
translation thus cannot fail.
translateEraMaybe :: (TranslateEra era f, TranslationError era f ~ ()) => TranslationContext era -> f (PreviousEra era) -> Maybe (f era) Source #
Variant of translateEra
for when TranslationError
is ()
, converting
the result to a Maybe
.