Add RDF.Guards is_statement/1 and is_quad/1

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](http://semver.org/) and
 ### Added
 
 - `RDF.Graph.new/2` and `RDF.Graph.add/2` support the addition of `RDF.Dataset`s
+- new guards in `RDF.Guards`: `is_statement/1` and `is_quad/1`
 
 ### Changed
 

lib/rdf/guards.ex

@@ -14,4 +14,15 @@ defmodule RDF.Guards do
   Returns if the given value is a triple, i.e. a tuple with three elements.
   """
   defguard is_triple(t) when is_tuple(t) and tuple_size(t) == 3
+
+  @doc """
+  Returns if the given value is a quad, i.e. a tuple with four elements.
+  """
+  defguard is_quad(q) when is_tuple(q) and tuple_size(q) == 4
+
+  @doc """
+  Returns if the given value is a triple or a quad
+  in terms of `is_triple/1` and `is_quad/1`.
+  """
+  defguard is_statement(s) when is_triple(s) or is_quad(s)
 end