87 lines
2.8 KiB
Elixir
87 lines
2.8 KiB
Elixir
defmodule RDF.Triple do
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@moduledoc """
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Defines a RDF Triple.
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A Triple is a plain Elixir tuple consisting of three valid RDF values for
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subject, predicate and object.
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"""
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alias RDF.{BlankNode, Literal}
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@type subject :: URI.t | BlankNode.t
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@type predicate :: URI.t
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@type object :: URI.t | BlankNode.t | Literal.t
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@type convertible_subject :: subject | atom | String.t
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@type convertible_predicate :: predicate | atom | String.t
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@type convertible_object :: object | atom | String.t # TODO: all basic Elixir types convertible to Literals
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defmodule InvalidSubjectError do
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defexception [:subject]
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def message(%{subject: subject}),
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do: "'#{inspect(subject)}' is not a valid subject of a RDF.Triple"
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end
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defmodule InvalidPredicateError do
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defexception [:predicate]
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def message(%{predicate: predicate}),
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do: "'#{inspect(predicate)}' is not a valid predicate of a RDF.Triple"
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end
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@doc """
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Creates a `RDF.Triple` with proper RDF values.
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An error is raised when the given elements are not convertible to RDF values.
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Note: The `RDF.triple` function is a shortcut to this function.
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# Examples
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iex> RDF.Triple.new("http://example.com/S", "http://example.com/p", 42)
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{RDF.uri("http://example.com/S"), RDF.uri("http://example.com/p"), RDF.literal(42)}
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"""
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def new(subject, predicate, object) do
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{
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convert_subject(subject),
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convert_predicate(predicate),
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convert_object(object)
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}
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end
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@doc """
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Creates a `RDF.Triple` with proper RDF values.
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An error is raised when the given elements are not convertible to RDF values.
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Note: The `RDF.triple` function is a shortcut to this function.
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# Examples
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iex> RDF.Triple.new {"http://example.com/S", "http://example.com/p", 42}
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{RDF.uri("http://example.com/S"), RDF.uri("http://example.com/p"), RDF.literal(42)}
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"""
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def new({subject, predicate, object}), do: new(subject, predicate, object)
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@doc false
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def convert_subject(uri)
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def convert_subject(uri = %URI{}), do: uri
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def convert_subject(bnode = %BlankNode{}), do: bnode
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def convert_subject(uri) when is_atom(uri) or is_binary(uri), do: RDF.uri(uri)
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def convert_subject(arg), do: raise InvalidSubjectError, subject: arg
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@doc false
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def convert_predicate(uri)
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def convert_predicate(uri = %URI{}), do: uri
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def convert_predicate(uri) when is_atom(uri) or is_binary(uri), do: RDF.uri(uri)
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def convert_predicate(arg), do: raise InvalidPredicateError, predicate: arg
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@doc false
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def convert_object(uri)
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def convert_object(uri = %URI{}), do: uri
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def convert_object(literal = %Literal{}), do: literal
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def convert_object(bnode = %BlankNode{}), do: bnode
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def convert_object(atom) when is_atom(atom), do: RDF.uri(atom)
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def convert_object(arg), do: Literal.new(arg)
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end
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