Add operator overloads for operation division, subtraction, and negation (#172)

src/ngraph/ops/divide.hpp

@@ -29,4 +29,9 @@ namespace ngraph
             virtual std::string description() const override { return "Divide"; }
         };
     }
+    inline std::shared_ptr<ngraph::Node> operator/(const std::shared_ptr<ngraph::Node> arg0,
+                                                   const std::shared_ptr<ngraph::Node> arg1)
+    {
+        return std::make_shared<ngraph::op::Divide>(arg0, arg1);
+    }
 }

src/ngraph/ops/negative.hpp

@@ -29,4 +29,8 @@ namespace ngraph
             virtual std::string description() const override { return "Negative"; }
         };
     }
+    inline std::shared_ptr<ngraph::Node> operator-(const std::shared_ptr<ngraph::Node> arg0)
+    {
+        return std::make_shared<ngraph::op::Negative>(arg0);
+    }
 }

src/ngraph/ops/subtract.hpp

@@ -29,4 +29,9 @@ namespace ngraph
             virtual std::string description() const override { return "Subtract"; }
         };
     }
+    inline std::shared_ptr<ngraph::Node> operator-(const std::shared_ptr<ngraph::Node> arg0,
+                                                   const std::shared_ptr<ngraph::Node> arg1)
+    {
+        return std::make_shared<ngraph::op::Subtract>(arg0, arg1);
+    }
 }