Elm.Print

This module defines prettyprinter for ElmDefinition type. and exports the function to represent it in the convenient way.

Documentation

prettyShowDefinition :: ElmDefinition -> Text

Pretty shows Elm types.

• See elmAliasDoc for examples of generated type alias.
• See elmTypeDoc for examples of generated type.

prettyShowEncoder :: ElmDefinition -> Text

Returns the encoder for the given type.

TODO +-------------------+------------------+-----------------+---------------------+ | Haskell Type | Eml Type | Encoder | JSON | +===================+==================+=================+=====================+ | Int | Int | standard encoder | | +-------------------+------------------+------------------+--------------------+

prettyShowDecoder :: ElmDefinition -> Text

• *Sum Types:**

Haskell type

type User
    = Foo
    | Bar String Int

Encoded JSON on Haskell side

    [ { "tag" : Foo
      }
    , { "tag" : Bar
      , "contents" : ["asd", 42, "qwerty"]
      }
    ]

Elm decoder

userDecoder : Decoder User
userDecoder =
    let decide : String -> Decoder User
        decide x = case x of
            Foo -> D.succeed Foo
            Bar -> D.field "contents" <| D.map2 Bar (D.index 0 D.string) (D.index 1 D.int)
            x -> D.fail <| "There is no constructor for User type:" ++ x
    in D.andThen decide (D.field "tag" D.string)

Standard missing encoders

encodeMaybe :: Text

encodeEither :: Text

encodePair :: Text

Standard missing decoders

decodeEnum :: Text

decodeChar :: Text

decodeEither :: Text

decodePair :: Text

Internal functions

elmAliasDoc :: ElmAlias -> Doc ann

Pretty printer for Elm aliases:

type alias User =
    { userHeh : String
    , userMeh : Int
    }

elmTypeDoc :: ElmType -> Doc ann

Pretty printer for Elm types with one or more constructors:

type Status a
    = Foo String Int
    | Bar a
    | Baz

If the type is a newtype then additionally unTYPENAME function is generated:

type Id a
    = Id String

unId : Id a -> String
unId (Id x) = x

If the type is Enum this function will add enum specific functions:

type Status
    = Approved
    | Yoyoyo
    | Wow

showStatus : Status -> String
showStatus x = case x of
    Approved -> Approved
    Yoyoyo -> Yoyoyo
    Wow -> Wow

readStatus : String -> Maybe Status
readStatus x = case x of
    Approved -> Just Approved
    Yoyoyo -> Just Yoyoyo
    Wow -> Just Wow
    _ -> Nothing

universeStatus : List Status
universeStatus = [Approved, Yoyoyo, Wow]