# `RDF.Star.Quad`
[🔗](https://github.com/rdf-elixir/rdf-ex/blob/v3.0.1/lib/rdf/star/quad.ex#L1)

Helper functions for RDF-star quads.

An RDF-star quad is represented as a plain Elixir tuple consisting of four valid
RDF values for subject, predicate, object and a graph name.
As opposed to an `RDF.Quad` the subject or object can be a triple.

# `coercible`

```elixir
@type coercible() ::
  {RDF.Star.Statement.coercible_subject(),
   RDF.Star.Statement.coercible_predicate(),
   RDF.Star.Statement.coercible_object(),
   RDF.Star.Statement.coercible_graph_name()}
```

# `t`

```elixir
@type t() ::
  {RDF.Star.Statement.subject(), RDF.Star.Statement.predicate(),
   RDF.Star.Statement.object(), RDF.Star.Statement.graph_name()}
```

# `new`

```elixir
@spec new(RDF.Star.Statement.coercible(), RDF.PropertyMap.t() | nil) :: t()
```

Creates a `RDF.Star.Quad` with proper RDF-star values.

An error is raised when the given elements are not coercible to RDF-star values.

Note: The `RDF.quad` function is a shortcut to this function.

## Examples

    iex> RDF.Star.Quad.new {"http://example.com/S", "http://example.com/p", 42, "http://example.com/Graph"}
    {~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42), ~I<http://example.com/Graph>}

    iex> RDF.Star.Quad.new {EX.S, EX.p, 42, EX.Graph}
    {RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}

    iex> RDF.Star.Quad.new {EX.S, EX.p, 42}
    {RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), nil}

    iex> RDF.Star.Quad.new {EX.S, :p, 42, EX.Graph}, RDF.PropertyMap.new(p: EX.p)
    {RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}

    iex> RDF.Star.Quad.new({{EX.S, :p, 42}, :p2, 43, EX.Graph}, RDF.PropertyMap.new(p: EX.p, p2: EX.p2))
    {{~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42)}, ~I<http://example.com/p2>, RDF.literal(43), ~I<http://example.com/Graph>}

# `new`

```elixir
@spec new(
  RDF.Star.Statement.coercible_subject(),
  RDF.Star.Statement.coercible_predicate(),
  RDF.Star.Statement.coercible_object(),
  RDF.Star.Statement.coercible_graph_name(),
  RDF.PropertyMap.t() | nil
) :: t()
```

Creates a `RDF.Star.Quad` with proper RDF-star values.

An error is raised when the given elements are not coercible to RDF-star values.

Note: The `RDF.quad` function is a shortcut to this function.

## Examples

    iex> RDF.Star.Quad.new("http://example.com/S", "http://example.com/p", 42, "http://example.com/Graph")
    {~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42), ~I<http://example.com/Graph>}

    iex> RDF.Star.Quad.new(EX.S, EX.p, 42, EX.Graph)
    {RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}

    iex> RDF.Star.Quad.new(EX.S, :p, 42, EX.Graph, RDF.PropertyMap.new(p: EX.p))
    {RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}

    iex> RDF.Star.Quad.new(EX.S, :p, 42, EX.Graph, RDF.PropertyMap.new(p: EX.p))
    {RDF.iri("http://example.com/S"), RDF.iri("http://example.com/p"), RDF.literal(42), RDF.iri("http://example.com/Graph")}

    iex> RDF.Star.Quad.new({EX.S, :p, 42}, :p2, 43, EX.Graph, RDF.PropertyMap.new(p: EX.p, p2: EX.p2))
    {{~I<http://example.com/S>, ~I<http://example.com/p>, RDF.literal(42)}, ~I<http://example.com/p2>, RDF.literal(43), ~I<http://example.com/Graph>}

# `valid?`

```elixir
@spec valid?(t() | any()) :: boolean()
```

Checks if the given tuple is a valid RDF quad.

The elements of a valid RDF-star quad must be RDF terms. On the subject position
only IRIs, blank nodes and triples are allowed, while on the predicate and graph name
position only IRIs allowed. The object position can be any RDF term or triple.

---

*Consult [api-reference.md](api-reference.md) for complete listing*