267 lines
8 KiB
Elixir
267 lines
8 KiB
Elixir
defmodule RDF.Literal do
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@moduledoc """
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RDF literals are leaf nodes of a RDF graph containing raw data, like strings and numbers.
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"""
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defstruct [:value, :uncanonical_lexical, :datatype, :language]
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@type t :: module
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alias RDF.Datatype.NS.XSD
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# to be able to pattern-match on plain types; we can't use RDF.Literal.Guards here since these aren't compiled here yet
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@xsd_string XSD.string
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@lang_string RDF.iri("http://www.w3.org/1999/02/22-rdf-syntax-ns#langString")
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@plain_types [@xsd_string, @lang_string]
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@doc """
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Creates a new `RDF.Literal` of the given value and tries to infer an appropriate XSD datatype.
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Note: The `RDF.literal` function is a shortcut to this function.
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The following mapping of Elixir types to XSD datatypes is applied:
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| Elixir datatype | XSD datatype |
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| :-------------- | :------------- |
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| `string` | `xsd:string` |
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| `boolean` | `xsd:boolean` |
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| `integer` | `xsd:integer` |
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| `float` | `xsd:double` |
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| `Time` | `xsd:time` |
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| `Date` | `xsd:date` |
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| `DateTime` | `xsd:dateTime` |
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| `NaiveDateTime` | `xsd:dateTime` |
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## Examples
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iex> RDF.Literal.new(42)
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%RDF.Literal{value: 42, datatype: XSD.integer}
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"""
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def new(value)
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def new(%RDF.Literal{} = literal), do: literal
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def new(value) when is_binary(value), do: RDF.String.new(value)
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def new(value) when is_boolean(value), do: RDF.Boolean.new(value)
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def new(value) when is_integer(value), do: RDF.Integer.new(value)
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def new(value) when is_float(value), do: RDF.Double.new(value)
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def new(%Date{} = value), do: RDF.Date.new(value)
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def new(%Time{} = value), do: RDF.Time.new(value)
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def new(%DateTime{} = value), do: RDF.DateTime.new(value)
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def new(%NaiveDateTime{} = value), do: RDF.DateTime.new(value)
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def new(value) do
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raise RDF.Literal.InvalidError, "#{inspect value} not convertible to a RDF.Literal"
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end
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@doc """
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Creates a new `RDF.Literal` with the given datatype or language tag.
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"""
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def new(value, opts)
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def new(value, opts) when is_list(opts),
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do: new(value, Map.new(opts))
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def new(value, %{language: nil} = opts),
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do: new(value, Map.delete(opts, :language))
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def new(value, %{language: _} = opts) do
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if is_binary(value) do
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if opts[:datatype] in [nil, @lang_string] do
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RDF.LangString.new(value, opts)
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else
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raise ArgumentError, "datatype with language must be rdf:langString"
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end
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else
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new(value, Map.delete(opts, :language)) # Should we raise a warning?
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end
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end
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def new(value, %{datatype: %RDF.IRI{} = id} = opts) do
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case RDF.Datatype.get(id) do
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nil -> %RDF.Literal{value: value, datatype: id}
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datatype -> datatype.new(value, opts)
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end
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end
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def new(value, %{datatype: datatype} = opts),
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do: new(value, %{opts | datatype: RDF.iri(datatype)})
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def new(value, opts) when is_map(opts) and map_size(opts) == 0,
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do: new(value)
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@doc """
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Creates a new `RDF.Literal`, but fails if it's not valid.
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Note: Validation is only possible if an `RDF.Datatype` with an implementation of
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`RDF.Datatype.valid?/1` exists.
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## Examples
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iex> RDF.Literal.new!("3.14", datatype: XSD.double) == RDF.Literal.new("3.14", datatype: XSD.double)
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true
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iex> RDF.Literal.new!("invalid", datatype: "http://example/unkown_datatype") == RDF.Literal.new("invalid", datatype: "http://example/unkown_datatype")
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true
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iex> RDF.Literal.new!("foo", datatype: XSD.integer)
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** (RDF.Literal.InvalidError) invalid RDF.Literal: %RDF.Literal{value: nil, lexical: "foo", datatype: ~I<http://www.w3.org/2001/XMLSchema#integer>}
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iex> RDF.Literal.new!("foo", datatype: RDF.langString)
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** (RDF.Literal.InvalidError) invalid RDF.Literal: %RDF.Literal{value: "foo", datatype: ~I<http://www.w3.org/1999/02/22-rdf-syntax-ns#langString>, language: nil}
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"""
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def new!(value, opts \\ %{}) do
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with %RDF.Literal{} = literal <- new(value, opts) do
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if valid?(literal) do
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literal
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else
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raise RDF.Literal.InvalidError, "invalid RDF.Literal: #{inspect literal}"
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end
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else
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invalid ->
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raise RDF.Literal.InvalidError, "invalid result of RDF.Literal.new: #{inspect invalid}"
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end
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end
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@doc """
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Returns the lexical representation of the given literal according to its datatype.
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"""
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def lexical(%RDF.Literal{value: value, uncanonical_lexical: nil, datatype: id} = literal) do
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case RDF.Datatype.get(id) do
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nil -> to_string(value)
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datatype -> datatype.lexical(literal)
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end
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end
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def lexical(%RDF.Literal{uncanonical_lexical: lexical}), do: lexical
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@doc """
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Returns the given literal in its canonical lexical representation.
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"""
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def canonical(%RDF.Literal{uncanonical_lexical: nil} = literal), do: literal
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def canonical(%RDF.Literal{datatype: id} = literal) do
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case RDF.Datatype.get(id) do
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nil -> literal
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datatype -> datatype.canonical(literal)
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end
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end
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@doc """
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Returns if the given literal is in its canonical lexical representation.
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"""
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def canonical?(%RDF.Literal{uncanonical_lexical: nil}), do: true
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def canonical?(_), do: false
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@doc """
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Returns if the value of the given literal is a valid according to its datatype.
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"""
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def valid?(%RDF.Literal{datatype: id} = literal) do
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case RDF.Datatype.get(id) do
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nil -> true
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datatype -> datatype.valid?(literal)
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end
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end
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@doc """
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Returns if a literal is a simple literal.
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A simple literal has no datatype or language.
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see <http://www.w3.org/TR/sparql11-query/#simple_literal>
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"""
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def simple?(%RDF.Literal{datatype: @xsd_string}), do: true
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def simple?(_), do: false
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@doc """
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Returns if a literal is a language-tagged literal.
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see <http://www.w3.org/TR/rdf-concepts/#dfn-plain-literal>
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"""
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def has_language?(%RDF.Literal{datatype: @lang_string}), do: true
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def has_language?(_), do: false
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@doc """
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Returns if a literal is a datatyped literal.
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For historical reasons, this excludes `xsd:string` and `rdf:langString`.
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see <http://www.w3.org/TR/rdf-concepts/#dfn-typed-literal>
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"""
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def has_datatype?(literal) do
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not plain?(literal) and not has_language?(literal)
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end
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@doc """
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Returns if a literal is a plain literal.
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A plain literal may have a language, but may not have a datatype.
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For all practical purposes, this includes `xsd:string` literals too.
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see <http://www.w3.org/TR/rdf-concepts/#dfn-plain-literal>
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"""
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def plain?(%RDF.Literal{datatype: datatype})
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when datatype in @plain_types, do: true
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def plain?(_), do: false
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def typed?(literal), do: not plain?(literal)
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@doc """
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Checks if two `RDF.Literal`s of this datatype are equal.
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Non-RDF terms are tried to be coerced via `RDF.Term.coerce/1` before comparison.
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Returns `nil` when the given arguments are not comparable as Literals.
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see <https://www.w3.org/TR/rdf-concepts/#section-Literal-Equality>
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"""
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def equal_value?(left, right)
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def equal_value?(%RDF.Literal{datatype: id1} = literal1, %RDF.Literal{datatype: id2} = literal2) do
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case RDF.Datatype.get(id1) do
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nil ->
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if id1 == id2 do
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literal1.value == literal2.value
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end
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datatype ->
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datatype.equal_value?(literal1, literal2)
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end
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end
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# TODO: Handle AnyURI in its own RDF.Datatype implementation
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@xsd_any_uri "http://www.w3.org/2001/XMLSchema#anyURI"
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def equal_value?(%RDF.Literal{datatype: %RDF.IRI{value: @xsd_any_uri}} = left, right),
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do: RDF.IRI.equal_value?(left, right)
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def equal_value?(left, %RDF.Literal{datatype: %RDF.IRI{value: @xsd_any_uri}} = right),
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do: RDF.IRI.equal_value?(left, right)
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def equal_value?(%RDF.Literal{} = left, right) when not is_nil(right) do
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unless RDF.Term.term?(right) do
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equal_value?(left, RDF.Term.coerce(right))
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end
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end
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def equal_value?(_, _), do: nil
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end
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defimpl String.Chars, for: RDF.Literal do
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def to_string(literal) do
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RDF.Literal.lexical(literal)
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end
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end
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