Morley.Michelson.Typed.Haskell.LooseSum

Representation of Haskell sum types via loosy typed Michelson values, useful for e.g. errors and enums.

In particular, ADT sum can be represented as constructor name + data it carries. Such expression does not have particular type because different constructors may carry different data, and we avoid lifting this data to a union in order to keep only the significant parts (and thus not to confuse the client).

Documentation

data ComposeResult a

Possible outcomes of an attempt to construct a Haskell ADT value from constructor name and relevant data.

Constructors

ComposeOk a

Composed fine.

ComposeCtorNotFound

No constructor with such name.

ComposeFieldTypeMismatch T T

Found required constructor, but type of data does not correspond to provided one.

Instances

Functor ComposeResult

Defined in Morley.Michelson.Typed.Haskell.LooseSum

Methods

fmap :: (a -> b) -> ComposeResult a -> ComposeResult b

(<$) :: a -> ComposeResult b -> ComposeResult a

Monoid (ComposeResult a)

Defined in Morley.Michelson.Typed.Haskell.LooseSum

Methods

mempty :: ComposeResult a

mappend :: ComposeResult a -> ComposeResult a -> ComposeResult a

mconcat :: [ComposeResult a] -> ComposeResult a

Semigroup (ComposeResult a)

Defined in Morley.Michelson.Typed.Haskell.LooseSum

Methods

(<>) :: ComposeResult a -> ComposeResult a -> ComposeResult a

sconcat :: NonEmpty (ComposeResult a) -> ComposeResult a

stimes :: Integral b => b -> ComposeResult a -> ComposeResult a

Show a => Show (ComposeResult a)

Defined in Morley.Michelson.Typed.Haskell.LooseSum

Methods

showsPrec :: Int -> ComposeResult a -> ShowS

show :: ComposeResult a -> String

showList :: [ComposeResult a] -> ShowS

fromTaggedVal :: LooseSumC dt => (Text, SomeValue) -> ComposeResult dt

Inverse to toTaggedVal.

>>> import Morley.Michelson.Typed

>>> fromTaggedVal @(Maybe ()) ("Just", SomeValue VUnit)
ComposeOk (Just ())

>>> data Foo = Foo () deriving Show
>>> fromTaggedVal @Foo ("Foo", SomeValue VUnit)
...
... GHC.Generics.Rep Foo
... is stuck. Likely
... Generic Foo
... instance is missing or out of scope.
...
>>> data Foo = Foo () deriving (Show, Generic)
>>> fromTaggedVal @Foo ("Foo", SomeValue VUnit)
ComposeOk (Foo ())

toTaggedVal :: LooseSumC dt => dt -> (Text, SomeValue)

Decompose Haskell type into constructor name and data it carries, converting the latter into Michelson Value.

>>> toTaggedVal $ Just ()
("Just",Constrained VUnit)

A custom TypeError is generated if a type doesn't have a Generic instance

>>> data Foo = Foo ()
>>> toTaggedVal $ Foo ()
...
... GHC.Generics.Rep Foo
... is stuck. Likely
... Generic Foo
... instance is missing or out of scope.
...
>>> data Foo = Foo () deriving Generic
>>> toTaggedVal $ Foo ()
("Foo",Constrained VUnit)

type LooseSumC dt = (NiceGeneric dt, GLooseSum (GRep dt))

Constraint for toTaggedVal and fromTaggedVal.