On Mon, Jul 20, 2009 at 7:24 PM, Igor R wrote:

In VC9.0 the following code gives the error message: 1>...\boost\tuple\detail\tuple_basic.hpp(419) : error C2259: 'Base' : cannot instantiate abstract class

If the Base is not abstract, the code compiles and works as expected. Unfortunately, I'm unable to realise why it tries to instantiate the Base, and how to overcome this issue, so any enlightenment would be greatly appreciated!

class Base { public:  virtual void close() = 0; };

class Derived : public Base { public:  void close()  {} };

#include

typedef boost::shared_ptr<Base> BasePtr; typedef boost::shared_ptr<BasePtr> BasePtrPtr;

#include #include

namespace bl = boost::lambda;

BasePtrPtr makeHolder(Base *base) {  return BasePtrPtr(new BasePtr(base), bl::bind(&Base::close, **bl::_1)); }

int main() {  Base *b = new Derived();  makeHolder(b);  return 0; }

The **bl::_1 (I suspect) results in a Base (eventually) rather than a Base& (which I guess is what you wanted). Using the fact that bind will take an object pointer (as opposed to an object/object reference), you can use this: return BasePtrPtr(new BasePtr(base), bl::bind(&Base::close, bl::bind(&BasePtr::get, bl::_1))); For some reason, *bl::_1 didn't want to compile. I'm making no guesses, so I just tried BasePtr::get, which I've used before (and compiles!) Stuart Dootson

Thanks to both of you! The one thing I still don't understand is how comes that the virtual function is called correctly (in case of non-abstract base) - the error message looks like some object "slicing" should occur in this binder, shouldn't it?