Toml.Codec.BiMap

Implementation of Tagged Partial Bidirectional Isomorphism. This module contains the BiMap type that represents conversion between two types with the possibility of failure.

See Toml.Codec.BiMap.Conversion for examples of BiMap with specific types. The BiMap concept is general and is not specific to TOML, but in this package most usages of BiMap are between TOML values and Haskell values.

BiMap concept

data BiMap e a b

Partial bidirectional isomorphism. BiMap a b contains two function:

1. a -> Either e b

2. b -> Either e a

If you think of types as sets then this data type can be illustrated by the following picture:

BiMap also implements Category typeclass. And this instance can be described clearly by this illustration:

Since: 0.4.0

Constructors

BiMap

Fields

• forward :: a -> Either e b
• backward :: b -> Either e a

Instances

Category (BiMap e :: Type -> Type -> Type)

Since: 0.4.0

Defined in Toml.Codec.BiMap

Methods

id :: forall (a :: k). BiMap e a a

(.) :: forall (b :: k) (c :: k) (a :: k). BiMap e b c -> BiMap e a b -> BiMap e a c

invert :: BiMap e a b -> BiMap e b a

Inverts bidirectional mapping.

Since: 0.4.0

iso :: (a -> b) -> (b -> a) -> BiMap e a b

Creates BiMap from isomorphism. Can be used in the following way:

newtype Even = Even Integer
newtype Odd  = Odd  Integer

succEven :: Even -> Odd
succEven (Even n) = Odd (n + 1)

predOdd :: Odd -> Even
predOdd (Odd n) = Even (n - 1)

_EvenOdd :: BiMap e Even Odd
_EvenOdd = iso succEven predOdd

Since: 0.4.0

prism

Arguments

:: (field -> object)

Constructor

-> (object -> Either error field)

Match object to either error or field

-> BiMap error object field

Creates BiMap from prism-like pair of functions. This combinator can be used to create BiMap for custom sum types like this:

data User
    = Admin  Integer  -- id of admin
    | Client Text     -- name of the client
    deriving (Show)

_Admin :: TomlBiMap User Integer
_Admin = Toml.prism Admin $ \case
    Admin i -> Right i
    other   -> Toml.wrongConstructor "Admin" other

_Client :: TomlBiMap User Text
_Client = Toml.prism Client $ \case
    Client n -> Right n
    other    -> Toml.wrongConstructor "Client" other

Since: 0.4.0

TOML BiMap

Type

type TomlBiMap = BiMap TomlBiMapError

BiMap specialized to TOML error.

Since: 1.0.0

Error

data TomlBiMapError

Type of errors for TOML BiMap.

Since: 1.0.0

Constructors

WrongConstructor

Error for cases with wrong constructors. For example, you're trying to convert Left but bidirectional converter expects Right.

Fields

• !Text

  Expected constructor name

• !Text

  Actual value

WrongValue

Error for cases with wrong values

Fields

• !MatchError

  Information about failed matching

ArbitraryError

Arbitrary textual error

Fields

• !Text

  Error message

Instances

Eq TomlBiMapError

Defined in Toml.Codec.BiMap

Methods

(==) :: TomlBiMapError -> TomlBiMapError -> Bool

(/=) :: TomlBiMapError -> TomlBiMapError -> Bool

Show TomlBiMapError

Defined in Toml.Codec.BiMap

Methods

showsPrec :: Int -> TomlBiMapError -> ShowS

show :: TomlBiMapError -> String

showList :: [TomlBiMapError] -> ShowS

Generic TomlBiMapError

Defined in Toml.Codec.BiMap

Associated Types

type Rep TomlBiMapError :: Type -> Type

Methods

from :: TomlBiMapError -> Rep TomlBiMapError x

to :: Rep TomlBiMapError x -> TomlBiMapError

NFData TomlBiMapError

Defined in Toml.Codec.BiMap

Methods

rnf :: TomlBiMapError -> ()

type Rep TomlBiMapError

Defined in Toml.Codec.BiMap

type Rep TomlBiMapError = D1 ('MetaData "TomlBiMapError" "Toml.Codec.BiMap" "tomland-1.3.3.0-inplace" 'False) (C1 ('MetaCons "WrongConstructor" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Text) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Text)) :+: (C1 ('MetaCons "WrongValue" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 MatchError)) :+: C1 ('MetaCons "ArbitraryError" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Text))))

wrongConstructor

Arguments

:: Show a

=> Text

Name of the expected constructor

-> a

Actual value

-> Either TomlBiMapError b

Helper to construct WrongConstuctor error.

Since: 1.0.0

prettyBiMapError :: TomlBiMapError -> Text

Converts TomlBiMapError into pretty human-readable text.

Since: 1.0.0

Smart constructors

mkAnyValueBiMap

Arguments

:: forall a (tag :: TValue). (forall (t :: TValue). Value t -> Either MatchError a)

Haskell type exctractor from Value

-> (a -> Value tag)

Convert Haskell type back to Value

-> TomlBiMap a AnyValue

Smart constructor for BiMap from a Haskell value (some primitive like Int or Text) to AnyValue.

Since: 0.4.0

Internals

tShow :: Show a => a -> Text