Add empty?/1 on Description, Graph and Dataset

CHANGELOG.md

@@ -11,6 +11,8 @@ This project adheres to [Semantic Versioning](http://semver.org/) and
 
 - a `RDF.Graph` builder DSL available under the `RDF.Graph.build/2` function
 - `RDF.Graph.new/2` and `RDF.Graph.add/2` support the addition of `RDF.Dataset`s
+- `RDF.Description.empty?/1`, `RDF.Graph.empty?/1` and `RDF.Dataset.empty?/1` which
+   are significantly faster than `Enum.empty?/1` 
 - new guards in `RDF.Guards`: `is_statement/1` and `is_quad/1`
 - `RDF.PropertyMap.terms/1` and `RDF.PropertyMap.iris/1`
 

lib/rdf/dataset.ex

@@ -656,6 +656,16 @@ defmodule RDF.Dataset do
     end)
   end
 
+  @doc """
+  Returns if the given `dataset` is empty.
+
+  Note: You should always prefer this over the use of `Enum.empty?/1` as it is significantly faster.
+  """
+  @spec empty?(t) :: boolean
+  def empty?(%__MODULE__{} = dataset) do
+    Enum.empty?(dataset.graphs) or dataset |> graphs() |> Enum.all?(&Graph.empty?/1)
+  end
+
   @doc """
   Checks if the given `input` statements exist within `dataset`.
 

lib/rdf/description.ex

@@ -637,6 +637,16 @@ defmodule RDF.Description do
 
   defdelegate count(description), to: __MODULE__, as: :statement_count
 
+  @doc """
+  Returns if the given `description` is empty.
+
+  Note: You should always prefer this over the use of `Enum.empty?/1` as it is significantly faster.
+  """
+  @spec empty?(t) :: boolean
+  def empty?(%__MODULE__{} = description) do
+    Enum.empty?(description.predications)
+  end
+
   @doc """
   Checks if the given `input` statements exist within `description`.
   """

lib/rdf/graph.ex

@@ -928,6 +928,16 @@ defmodule RDF.Graph do
 
   defdelegate statements(graph, opts \\ []), to: __MODULE__, as: :triples
 
+  @doc """
+  Returns if the given `graph` is empty.
+
+  Note: You should always prefer this over the use of `Enum.empty?/1` as it is significantly faster.
+  """
+  @spec empty?(t) :: boolean
+  def empty?(%__MODULE__{} = graph) do
+    Enum.empty?(graph.descriptions)
+  end
+
   @doc """
   Checks if the given `input` statements exist within `graph`.
   """

test/unit/dataset_test.exs

@@ -1621,6 +1621,12 @@ defmodule RDF.DatasetTest do
     assert Dataset.statement_count(Dataset.new(statement())) == 1
   end
 
+  test "empty?/1" do
+    assert Dataset.empty?(dataset()) == true
+    assert Dataset.empty?(Dataset.new(statement())) == false
+    assert Dataset.empty?(Dataset.new(graph())) == true
+  end
+
   describe "include?/3" do
     test "valid cases" do
       dataset =

test/unit/description_test.exs

@@ -792,6 +792,11 @@ defmodule RDF.DescriptionTest do
     assert Description.statement_count(description({EX.p(), EX.O})) == 1
   end
 
+  test "empty?/1" do
+    assert Description.empty?(Description.new(EX.S)) == true
+    assert Description.empty?(description({EX.p(), EX.O})) == false
+  end
+
   describe "include?/3" do
     test "valid cases" do
       desc =

test/unit/graph_test.exs

@@ -1288,6 +1288,11 @@ defmodule RDF.GraphTest do
     assert Graph.statement_count(Graph.new(statement())) == 1
   end
 
+  test "empty?/1" do
+    assert Graph.empty?(graph()) == true
+    assert Graph.empty?(Graph.new(statement())) == false
+  end
+
   describe "include?/3" do
     test "valid cases" do
       graph =