+/*
+ implement Class::constructor, a SCM function that
+ returns an encapsulated factory function.
+ */
+#define IMPLEMENT_CTOR_CALLBACK(Class) \
+static void * \
+Class ## _ctor (SCM) \
+{ \
+ return new Class ; \
+} \
+SCM Class :: constructor_cxx_function;\
+void \
+Class ## _constructor_init() \
+{ \
+ SCM s = smobify_cxx_function (& Class ## _ctor); \
+ scm_permanent_object (s);\
+ gh_define (#Class "::constructor", s);\
+ Class :: constructor_cxx_function = s;\
+}\
+ADD_SCM_INIT_FUNC(Class ## _ctor_init, Class ## _constructor_init);
+