+{ return dynamic_cast<const T *>(&obj) != 0; }
+
+
+class basic;
+
+/** Base class for print_functor handlers */
+class print_functor_impl {
+public:
+ virtual ~print_functor_impl() {}
+ virtual print_functor_impl *duplicate() const = 0;
+ virtual void operator()(const basic & obj, const print_context & c, unsigned level) const = 0;
+};
+
+/** print_functor handler for pointer-to-functions of class T, context type C */
+template <class T, class C>
+class print_ptrfun_handler : public print_functor_impl {
+public:
+ typedef void (*F)(const T &, const C &, unsigned);
+
+ print_ptrfun_handler(F f_) : f(f_) {}
+ print_ptrfun_handler *duplicate() const { return new print_ptrfun_handler(*this); }
+
+ void operator()(const basic & obj, const print_context & c, unsigned level) const
+ {
+ // Call the supplied function
+ f(dynamic_cast<const T &>(obj), dynamic_cast<const C &>(c), level);
+ }
+
+private:
+ F f;
+};
+
+/** print_functor handler for member functions of class T, context type C */
+template <class T, class C>
+class print_memfun_handler : public print_functor_impl {
+public:
+ typedef void (T::*F)(const C & c, unsigned level);
+
+ print_memfun_handler(F f_) : f(f_) {}
+ print_memfun_handler *duplicate() const { return new print_memfun_handler(*this); }
+
+ void operator()(const basic & obj, const print_context & c, unsigned level) const
+ {
+ // Call the supplied member function
+ return (dynamic_cast<const T &>(obj).*f)(dynamic_cast<const C &>(c), level);
+ }
+
+private:
+ F f;
+};
+
+/** This class represents a print method for a certain algebraic class and
+ * print_context type. Its main purpose is to hide the difference between
+ * member functions and nonmember functions behind one unified operator()
+ * interface. print_functor has value semantics and acts as a smart pointer
+ * (with deep copy) to a class derived from print_functor_impl which
+ * implements the actual function call. */
+class print_functor {
+public:
+ print_functor() : impl(0) {}
+ print_functor(const print_functor & other) : impl(other.impl.get() ? other.impl->duplicate() : 0) {}
+ print_functor(std::auto_ptr<print_functor_impl> impl_) : impl(impl_) {}
+
+ template <class T, class C>
+ print_functor(void f(const T &, const C &, unsigned)) : impl(new print_ptrfun_handler<T, C>(f)) {}
+
+ template <class T, class C>
+ print_functor(void (T::*f)(const C &, unsigned)) : impl(new print_memfun_handler<T, C>(f)) {}
+
+ print_functor & operator=(const print_functor & other)
+ {
+ if (this != &other) {
+ print_functor_impl *p = other.impl.get();
+ impl.reset(p ? other.impl->duplicate() : 0);
+ }
+ return *this;
+ }
+
+ void operator()(const basic & obj, const print_context & c, unsigned level) const
+ {
+ (*impl)(obj, c, level);
+ }
+
+ bool is_valid() const { return impl.get(); }
+
+private:
+ std::auto_ptr<print_functor_impl> impl;
+};
+