Re: [Boost-users] [bind] using NULL as a bound argument

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-06-16 14:40:35

Marc Horowitz:

>I am attempting to use Boost.Bind to create a callable where some of
> the bound arguments might be NULL.  Here is a simple example:
>
>    void f(const char *) {}
>
>    int main()
>    {
>      (std::tr1::bind(f, _1))(NULL);
>
>      return(0);
>    }

This is indeed annoying. I've also been using

>    class NullPlaceholder
>    {
>    public:
>      template <class T>
>      operator T*() const { return((T*)NULL); }
>    };
>
>    NullPlaceholder _NULL;

except not calling it _NULL since this name is reserved.

We should probably have boost/nullptr.hpp that defines the macro nullptr to 
something like (::boost::nullptr_t()) in C++03 mode and does nothing 
otherwise (as C++0x will have a nullptr keyword.)

shared_ptr will also need a nullptr_t type when it's updated to match the 
C++0x interface.