From f9942b13158c5e4a522d31ffa87a4c9cf0e78e1a Mon Sep 17 00:00:00 2001
From: Marcel Otto <marcelotto@gmx.de>
Date: Fri, 8 Apr 2022 03:23:16 +0200
Subject: [PATCH] Add RDF.Data.empty?/1

---
 CHANGELOG.md            |  7 +++++--
 lib/rdf/data.ex         | 11 +++++++++++
 test/unit/data_test.exs | 15 +++++++++++++++
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 49e2a8d..8562880 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,8 +11,11 @@ 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` 
+- `RDF.Description.empty?/1`, `RDF.Graph.empty?/1`, `RDF.Dataset.empty?/1` and
+  `RDF.Data.empty?/1` which are significantly faster than `Enum.empty?/1`
+  - By replacing all `Enum.empty?/1` uses over the RDF data structures with these    
+    new `empty?/1` functions throughout the code base, several functions benefit
+    from this performance improvement.
 - `RDF.Description.first/2` now has a `RDF.Description.first/3` variant which
   supports a default value
 - new guards in `RDF.Guards`: `is_statement/1` and `is_quad/1`
diff --git a/lib/rdf/data.ex b/lib/rdf/data.ex
index c9cd831..f0372b6 100644
--- a/lib/rdf/data.ex
+++ b/lib/rdf/data.ex
@@ -31,6 +31,11 @@ defprotocol RDF.Data do
   """
   def pop(data)
 
+  @doc """
+  Returns if the given RDF data structure is empty.
+  """
+  def empty?(data)
+
   @doc """
   Checks if the given statement exists within a RDF data structure.
   """
@@ -175,6 +180,8 @@ defimpl RDF.Data, for: RDF.Description do
 
   def pop(description), do: Description.pop(description)
 
+  def empty?(description), do: Description.empty?(description)
+
   def include?(description, input, opts \\ []),
     do: Description.include?(description, input, opts)
 
@@ -275,6 +282,8 @@ defimpl RDF.Data, for: RDF.Graph do
 
   def pop(graph), do: Graph.pop(graph)
 
+  def empty?(graph), do: Graph.empty?(graph)
+
   def include?(graph, input, opts \\ []), do: Graph.include?(graph, input, opts)
 
   def describes?(graph, subject),
@@ -343,6 +352,8 @@ defimpl RDF.Data, for: RDF.Dataset do
 
   def pop(dataset), do: Dataset.pop(dataset)
 
+  def empty?(dataset), do: Dataset.empty?(dataset)
+
   def include?(dataset, input, opts), do: Dataset.include?(dataset, input, opts)
 
   def describes?(dataset, subject),
diff --git a/test/unit/data_test.exs b/test/unit/data_test.exs
index 068c945..a20d17e 100644
--- a/test/unit/data_test.exs
+++ b/test/unit/data_test.exs
@@ -90,6 +90,11 @@ defmodule RDF.DataTest do
       assert RDF.Data.pop(description) == Description.pop(description)
     end
 
+    test "empty?", %{description: description} do
+      assert RDF.Data.empty?(description) == false
+      assert RDF.Data.empty?(RDF.description(EX.S)) == true
+    end
+
     test "include?", %{description: description} do
       assert RDF.Data.include?(description, {EX.S, EX.p1(), EX.O2})
       refute RDF.Data.include?(description, {EX.Other, EX.p1(), EX.O2})
@@ -258,6 +263,11 @@ defmodule RDF.DataTest do
       assert RDF.Data.pop(graph) == Graph.pop(graph)
     end
 
+    test "empty?", %{graph: graph} do
+      assert RDF.Data.empty?(graph) == false
+      assert RDF.Data.empty?(RDF.graph()) == true
+    end
+
     test "include?", %{graph: graph} do
       assert RDF.Data.include?(graph, {EX.S, EX.p1(), EX.O2})
       assert RDF.Data.include?(graph, {EX.S2, EX.p2(), EX.O3})
@@ -419,6 +429,11 @@ defmodule RDF.DataTest do
       assert RDF.Data.pop(dataset) == Dataset.pop(dataset)
     end
 
+    test "empty?", %{dataset: dataset} do
+      assert RDF.Data.empty?(dataset) == false
+      assert RDF.Data.empty?(RDF.dataset()) == true
+    end
+
     test "include?", %{dataset: dataset} do
       assert RDF.Data.include?(dataset, {EX.S, EX.p1(), EX.O2})
       assert RDF.Data.include?(dataset, {EX.S2, EX.p2(), EX.O3})