Re: [boost] bind/lambda - unsupported use case?

From: Aleksey Gurtovoy (agurtovoy_at_[hidden])
Date: 2003-08-10 20:47:38

Peter Dimov wrote:
> Aleksey Gurtovoy wrote:
> > Consider the following snippet:
> >
> >     void show_warning( message_dialog const&, user_message );
> >     void post_command( boost::function<void()> );
> >
> >     int main()
> >     {
> >         boost::function<void( user_message )> f(
> >               bind( &post_command
> >                 , ????( bind( &show_warning, message_dialog(), _1 ) )
> >     //            ^^^^ what goes here?
> 
> "protect", in boost/bind/protect.hpp. Lambda has both "protect" and
> "unlambda", either will work (I think).
> 
> >                 )
> >             );
> >     }

I am afraid it's not that simple. Note that 'post_command' takes a 
_nullary_, not an unary function. To clarify the semantics of the above,
I need to construct a bind expression which would allow the original code
to become equivalent to the following:

    void
    post_show_warning_command( 
          message_dialog const& a_dialog
        , user_message          a_message
        )
    {
        post_command( boost::bind( &show_warning
            , a_dialog
            , a_message
            ) );
    }

    int main()
    {
        boost::function<void( user_message )> f( 
              boost::bind( 
                  &post_show_warning_command
                , message_dialog()
                , _1
                )
            );
    }
    

Aleksey