60 lines
1.4 KiB
Elixir
60 lines
1.4 KiB
Elixir
defmodule RDF.BlankNode do
|
|
@moduledoc """
|
|
A RDF blank node (aka bnode) is a local node of a graph without an IRI.
|
|
|
|
see <https://www.w3.org/TR/rdf11-primer/#section-blank-node>
|
|
and <https://www.w3.org/TR/rdf11-concepts/#section-blank-nodes>
|
|
"""
|
|
|
|
@type t :: %__MODULE__{
|
|
value: String.t()
|
|
}
|
|
|
|
@enforce_keys [:value]
|
|
defstruct [:value]
|
|
|
|
@doc """
|
|
Creates a `RDF.BlankNode`.
|
|
"""
|
|
@spec new :: t
|
|
def new,
|
|
do: new(make_ref())
|
|
|
|
@doc """
|
|
Creates a `RDF.BlankNode` with a user-defined value for its identity.
|
|
|
|
## Examples
|
|
|
|
iex> RDF.bnode(:foo)
|
|
%RDF.BlankNode{value: "foo"}
|
|
"""
|
|
@spec new(reference | String.t() | atom | integer) :: t
|
|
def new(value)
|
|
|
|
def new(value) when is_binary(value),
|
|
do: %__MODULE__{value: value}
|
|
|
|
def new(value) when is_reference(value),
|
|
do: value |> :erlang.ref_to_list() |> to_string |> String.replace(~r/\<|\>/, "") |> new
|
|
|
|
def new(value) when is_atom(value) or is_integer(value),
|
|
do: value |> to_string |> new
|
|
|
|
@doc """
|
|
Tests for value equality of blank nodes.
|
|
|
|
Returns `nil` when the given arguments are not comparable as blank nodes.
|
|
"""
|
|
@spec equal_value?(t, t) :: boolean | nil
|
|
def equal_value?(left, right)
|
|
|
|
def equal_value?(%__MODULE__{value: left}, %__MODULE__{value: right}),
|
|
do: left == right
|
|
|
|
def equal_value?(_, _),
|
|
do: nil
|
|
|
|
defimpl String.Chars do
|
|
def to_string(bnode), do: "_:#{bnode.value}"
|
|
end
|
|
end
|