Add Decimal implementation of RDF.Term protocol

lib/rdf/term.ex

@@ -100,6 +100,12 @@ defimpl RDF.Term, for: Float do
   def coerce(term),               do: RDF.Double.new(term)
 end
 
+defimpl RDF.Term, for: Decimal do
+  def equal?(term1, term2),       do: term1 == term2
+  def equal_value?(term1, term2), do: RDF.Term.equal_value?(coerce(term1), term2)
+  def coerce(term),               do: RDF.Decimal.new(term)
+end
+
 defimpl RDF.Term, for: DateTime do
   def equal?(term1, term2),       do: term1 == term2
   def equal_value?(term1, term2), do: RDF.Term.equal_value?(coerce(term1), term2)

test/unit/equality_test.exs

@@ -2,7 +2,7 @@ defmodule RDF.EqualityTest do
   use RDF.Test.Case
 
   alias RDF.NS.XSD
-
+  alias Decimal, as: D
 
   describe "RDF.IRI" do
     @term_equal_iris [
@@ -185,13 +185,17 @@ defmodule RDF.EqualityTest do
     @value_equal_numerics_by_coercion [
       {RDF.integer(42),   42},
       {RDF.integer(42),   42.0},
+      {RDF.integer(42),   D.new(42)},
       {RDF.decimal(42),   42},
       {RDF.decimal(3.14), 3.14},
+      {RDF.decimal(3.14), D.new(3.14)},
       {RDF.double(42),    42},
       {RDF.double(3.14),  3.14},
+      {RDF.double(3.14),  D.new(3.14)},
     ]
     @value_unequal_numerics_by_coercion [
       {RDF.integer(3),    3.14},
+      {RDF.integer(3),    D.new(3.14)},
       {RDF.double(3.14),  3},
       {RDF.decimal(3.14), 3},
     ]

test/unit/term_test.exs

@@ -3,6 +3,8 @@ defmodule RDF.TermTest do
 
   doctest RDF.Term
 
+  alias Decimal, as: D
+
   describe "coerce/1" do
     test "with RDF.IRI" do
       assert RDF.Term.coerce(~I<http://example.com/>) == ~I<http://example.com/>
@@ -33,6 +35,10 @@ defmodule RDF.TermTest do
       assert RDF.Term.coerce(3.14) == RDF.double(3.14)
     end
 
+    test "with decimal" do
+      assert D.new(3.14) |> RDF.Term.coerce() == RDF.decimal(3.14)
+    end
+
     test "with datetime" do
       assert DateTime.from_iso8601("2002-04-02T12:00:00+00:00") |> elem(1) |> RDF.Term.coerce() ==
              DateTime.from_iso8601("2002-04-02T12:00:00+00:00") |> elem(1) |> RDF.datetime()