Re: [boost] Forwarding Problem (was: [smart_ptr] operator ->*)

From: Peter Dimov (pdimov_at_[hidden])
Date: 2006-05-24 04:58:16

Paul Mensonides wrote:

[...]

> template<class T, class M, class C> inline
> typename closure<M C::*>::type operator->*(const std::auto_ptr<T>&
> sp, M C::* member) {
>    return make_closure(&*sp, member);
> }

[...]

> Basically, the implementation above does all the work necessary to
> implement operator->* once and for all (for any number of different
> smart pointers).  The only things that one might need to change for a
> particular smart pointer is how the smart pointer is passed to
> operator->* and how the raw pointer is accessed:
>
> template<class T, class M, class C> inline
> typename closure<M C::*>::type operator->*(boost::shared_ptr<T> sp, M
> C::* member) {
>    return make_closure(sp.get(), member);
> }
>
> template<class T> class smart_ptr {
>    // ...
>    public:
>        template<class M, class C> inline
>        typename closure<M C::*>::type operator->*(M C::* member) {
>            return make_closure(get(), member);
>        }
>    // ...
> };

You don't have to change the implementation of ->* depending on the smart 
pointer type. *p is always the dereference operation, and (proxy references 
notwithstanding) &*p is always a raw pointer to the pointee. get() is needed 
for cases when the source is NULL, but we need not worry about them here, 
as ->* isn't allowed.

So:

template<class P, class M, class C> inline
typename closure<M C::*>::type operator->*( P p, M C::* member)
{
    return make_closure( &*p, member );
}

It would work for iterators, too.