From fd3a20116bc7e2e2dd88287923c79e429b6719a5 Mon Sep 17 00:00:00 2001
From: Marcel Otto <marcelotto@gmx.de>
Date: Fri, 31 Mar 2017 16:04:39 +0200
Subject: [PATCH] core: creating a new graph from another graph

---
 lib/rdf/graph.ex         | 12 ++++++++++++
 test/unit/graph_test.exs | 20 ++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/lib/rdf/graph.ex b/lib/rdf/graph.ex
index e904c50..17cb714 100644
--- a/lib/rdf/graph.ex
+++ b/lib/rdf/graph.ex
@@ -38,6 +38,12 @@ defmodule RDF.Graph do
   def new(%RDF.Description{} = description),
     do: new() |> add(description)
 
+  @doc """
+  Creates an unnamed `RDF.Graph` from another `RDF.Graph`.
+  """
+  def new(%RDF.Graph{descriptions: descriptions}),
+    do: %RDF.Graph{descriptions: descriptions}
+
   @doc """
   Creates an empty unnamed `RDF.Graph`.
   """
@@ -68,6 +74,12 @@ defmodule RDF.Graph do
   def new(name, %RDF.Description{} = description),
     do: new(name) |> add(description)
 
+  @doc """
+  Creates a named `RDF.Graph` from another `RDF.Graph`.
+  """
+  def new(name, %RDF.Graph{descriptions: descriptions}),
+    do: %RDF.Graph{new(name) | descriptions: descriptions}
+
   @doc """
   Creates an unnamed `RDF.Graph` with initial triples.
   """
diff --git a/test/unit/graph_test.exs b/test/unit/graph_test.exs
index 95a8b48..68d5bf8 100644
--- a/test/unit/graph_test.exs
+++ b/test/unit/graph_test.exs
@@ -77,6 +77,26 @@ defmodule RDF.GraphTest do
       assert unnamed_graph?(g)
       assert graph_includes_statement?(g, {EX.Subject, EX.predicate, EX.Object})
     end
+
+    test "creating a named graph from another graph" do
+      g = Graph.new(EX.GraphName, Graph.new({EX.Subject, EX.predicate, EX.Object}))
+      assert named_graph?(g, uri(EX.GraphName))
+      assert graph_includes_statement?(g, {EX.Subject, EX.predicate, EX.Object})
+
+      g = Graph.new(EX.GraphName, Graph.new(EX.OtherGraphName, {EX.Subject, EX.predicate, EX.Object}))
+      assert named_graph?(g, uri(EX.GraphName))
+      assert graph_includes_statement?(g, {EX.Subject, EX.predicate, EX.Object})
+    end
+
+    test "creating an unnamed graph from another graph" do
+      g = Graph.new(Graph.new({EX.Subject, EX.predicate, EX.Object}))
+      assert unnamed_graph?(g)
+      assert graph_includes_statement?(g, {EX.Subject, EX.predicate, EX.Object})
+
+      g = Graph.new(Graph.new(EX.OtherGraphName, {EX.Subject, EX.predicate, EX.Object}))
+      assert unnamed_graph?(g)
+      assert graph_includes_statement?(g, {EX.Subject, EX.predicate, EX.Object})
+    end
   end
 
   describe "adding triples" do