Export new LazyObject interface (#574)

SWIG/instruments.i

@@ -24,6 +24,7 @@
 %include types.i
 %include marketelements.i
 %include observer.i
+%include lazyobject.i
 %include stl.i
 
 // pricing engine
@@ -45,15 +46,12 @@ using QuantLib::Instrument;
 %}
 
 %shared_ptr(Instrument)
-class Instrument : public Observable {
+class Instrument : public LazyObject {
   public:
     Real NPV() const;
     Real errorEstimate() const;
     bool isExpired() const;
     void setPricingEngine(const ext::shared_ptr<PricingEngine>&);
-    void recalculate();
-    void freeze();
-    void unfreeze();
   private:
     Instrument();
 };

SWIG/lazyobject.i

@@ -0,0 +1,53 @@
+
+/*
+ Copyright (C) 2000, 2001, 2002, 2003 RiskMap srl
+ Copyright (C) 2018 Matthias Lungwitz
+
+ This file is part of QuantLib, a free-software/open-source library
+ for financial quantitative analysts and developers - http://quantlib.org/
+
+ QuantLib is free software: you can redistribute it and/or modify it
+ under the terms of the QuantLib license.  You should have received a
+ copy of the license along with this program; if not, please email
+ <[email protected]>. The license is also available online at
+ <http://quantlib.org/license.shtml>.
+
+ This program is distributed in the hope that it will be useful, but WITHOUT
+ ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ FOR A PARTICULAR PURPOSE.  See the license for more details.
+*/
+
+#ifndef quantlib_lazy_object_i
+#define quantlib_lazy_object_i
+
+%include common.i
+%include types.i
+%include observer.i
+
+%{
+using QuantLib::LazyObject;
+%}
+
+%shared_ptr(LazyObject)
+class LazyObject : public Observable {
+  private:
+    LazyObject();
+  public:
+    void recalculate();
+    void freeze();
+    void unfreeze();
+    %extend {
+        static void forwardFirstNotificationOnly() {
+            LazyObject::Defaults::instance().forwardFirstNotificationOnly();
+        }
+        static void alwaysForwardNotifications() {
+            LazyObject::Defaults::instance().alwaysForwardNotifications();
+        }
+        static bool forwardsAllNotifications() {
+            return LazyObject::Defaults::instance().forwardsAllNotifications();
+        }
+    }
+};
+
+
+#endif

SWIG/ql.i

@@ -150,6 +150,7 @@ QL_DEPRECATED_DISABLE_WARNING
 %include integrals.i
 %include interestrate.i
 %include interpolation.i
+%include lazyobject.i
 %include linearalgebra.i
 %include localvolatilities.i
 %include lmm.i