Generics.Eot

generics-eot tries to be a library for datatype generic programming that is easy to understand. "eot" stands for "eithers of tuples".

A tutorial on how to use generics-eot can be found here: Generics.Eot.Tutorial.

Documentation

class HasEot a where

An instance (HasEot a) allows us to

• convert values of an arbitrary algebraic datatype a to and from a generic representation (Eot a) (see toEot and fromEot).
• extract meta information about the type a (see datatype).

Once an algebraic datatype has an instance for Generic it automatically gets one for HasEot.

Associated Types

type Eot a :: *

Eot is a type level function that maps arbitrary ADTs to isomorphic generic representations. Here's an example:

data Foo = A Int Bool | B String

would be mapped to:

Either (Int, (Bool, ())) (Either (String, ()) Void)

These representations follow these rules:

• The choice between constructors is mapped to right-nested Eithers.
• There's always a so-called end-marker Void. It's an invalid choice (and Void is uninhabited to make sure you don't accidentally create such a value). So e.g. data Foo = A would be mapped to Either () Void, and a type with no constructors is mapped to Void.
• The fields of one constructor are mapped to right-nested tuples.
• Again there's always an end-marker, this time of type (). A constructor with three fields a, b, c is mapped to (a, (b, (c, ()))), one field a is mapped to (a, ()), and no fields are mapped to () (just the end-marker).

These rules (and the end-markers) are necessary to make sure generic functions know exactly which parts of the generic representation are field types and which parts belong to the generic skeleton.

Methods

toEot :: a -> Eot a

Convert a value of type a to its generic representation.

fromEot :: Eot a -> a

Convert a value in a generic representation to a (inverse of toEot).

datatype :: Proxy a -> Datatype

Extract meta information about the ADT.

Instances

(Generic a, ImpliedByGeneric a c f) => HasEot a

Meta Information

data Datatype

Type for meta information about ADTs.

Constructors

Datatype

Fields

datatypeName :: String

unqualified name of the type

constructors :: [Constructor]

Instances

Eq Datatype

Show Datatype

EotCreateTableStatement [String] fields => EotCreateTableStatement Datatype (Either fields Void)

data Constructor

Constructors

Constructor

Fields

constructorName :: String

fields :: Fields

Instances

Eq Constructor

Show Constructor

data Fields

Type that represents meta information about fields of one constructor.

Constructors

Selectors [String]

Record constructor, containing the list of the selector names.

NoSelectors Int

Constructor with fields, but without selector names. The argument gives the number of fields.

NoFields

Constructor without fields.

Instances

Eq Fields

Show Fields

Void

data Void

Uninhabited type.

Instances

Eq Void

Ord Void

Show Void

Generic Void

EotDeserialize Void

EotSerialize Void

EotCreateTableStatement [String] fields => EotCreateTableStatement Datatype (Either fields Void)

type Rep Void

Useful Re-exports

class Generic a

Representable types of kind *. This class is derivable in GHC with the DeriveGeneric flag on.

Minimal complete definition

from, to

Instances

Generic Bool

Generic Char

Generic Double

Generic Float

Generic Int

Generic Ordering

Generic ()

Generic All

Generic Any

Generic Arity

Generic Fixity

Generic Associativity

Generic Void

Generic C

Generic NoSelectors

Generic Person

Generic B

Generic A

Generic [a]

Generic (U1 p)

Generic (Par1 p)

Generic (ZipList a)

Generic (Dual a)

Generic (Endo a)

Generic (Sum a)

Generic (Product a)

Generic (First a)

Generic (Last a)

Generic (Maybe a)

Generic (Either a b)

Generic (Rec1 f p)

Generic (a, b)

Generic (Const a b)

Generic (WrappedMonad m a)

Generic (Proxy * t)

Generic (K1 i c p)

Generic ((:+:) f g p)

Generic ((:*:) f g p)

Generic ((:.:) f g p)

Generic (a, b, c)

Generic (WrappedArrow a b c)

Generic (Alt k f a)

Generic (M1 i c f p)

Generic (a, b, c, d)

Generic (a, b, c, d, e)

Generic (a, b, c, d, e, f)

Generic (a, b, c, d, e, f, g)

data Proxy t :: k -> *

A concrete, poly-kinded proxy type

Constructors

Proxy

Instances

Monad (Proxy *)

Functor (Proxy *)

Applicative (Proxy *)

Foldable (Proxy *)

Bounded (Proxy k s)

Enum (Proxy k s)

Eq (Proxy k s)

Ord (Proxy k s)

Read (Proxy k s)

Show (Proxy k s)

Ix (Proxy k s)

Generic (Proxy * t)

Monoid (Proxy k s)

type Rep (Proxy k t) = D1 D1Proxy (C1 C1_0Proxy U1)