Awesome

Eden

edn (extensible data notation) encoder/decoder implemented in Elixir.

Usage

Include Eden as a dependency in your Elixir project by adding it in your deps list:

def deps do
  [{:eden, "~> 0.1.2"}]
end

Eden is a library application and as such doesn't specify an application callback module. Even so, if you would like to build a release that includes Eden, you need to add it as an application dependency in your mix.exs:

  def application do
    [applications: [:eden]]
  end

Examples

iex> Eden.encode([1, 2])
{:ok, "(1, 2)"}

iex> Eden.encode(%{a: 1, b: 2, c: 3})
{:ok, "{:a 1, :b 2, :c 3}"}

iex> Eden.encode({:a, 1})
{:error, Protocol.UndefinedError}

iex> Eden.decode("{:a 1 :b 2}")
{:ok, %{a: 1, b: 2}}

iex> Eden.decode("(hello :world \\!)")
{:ok, [%Eden.Symbol{name: "hello"}, :world, %Eden.Character{char: "!"}]

iex> Eden.decode("[1 2 3 4]")
{:ok, #Array<[1, 2, 3, 4], fixed=false, default=nil>}

iex> Eden.decode("nil true false")
{:ok, [nil, true, false]}

iex> Eden.decode("nil true false .")
{:error, Eden.Exception.UnexpectedInputError}

Data Structures Mapping: edn <-> Elixir

Further Considerations

Character

There is no way of distinguishing a common integer from the representation of a character in a String or in Char lists. This forces the creation of a new representation for this type so it can be correctly translated from and to edn.

Arbitrary Precision Integer and Float

The Erlang VM (EVM) only provides arbitrary precision integers so all integers will be of this type this and the N modifier will be ignored when parsing an edn integer.

On the other hand native arbitrary precision floating point numbers are not provided by the EVM so all values of type float will be represented according to what the EVM supports.

Keyword and Symbol Representation

On one hand the decision to translate edn keywords as Elixir atoms comes from the fact these two data types are given a similar usage on both languages. On the other, it might get awkward really fast using a new Eden.Symbol struct as the representation for edn's symbols so this might change.

vector

There is no constant lookup or nearly constant indexed data structure like edn's vector other than the :array data structure implemented in one of Erlang's standard library modules. Until there is a better implementation for this Eden will use Array, an Elixir wrapper library for Erlang's array.

edn grammar

expr -> literal | map | list | vector | tagged_value

literal -> nil | true | false | keyword | symbol | integer | float | string

map -> { pair* }
pair -> expr expr

list -> ( expr* )

vector -> [ expr* ]

tagged_value -> tag expr