Re: [boost] Pimpl Again?

Peter Dimov writes:

Howard Hinnant wrote:

...

It has to be outlined, in the source.cpp:

class Book { struct implementation; std::unique_ptr<implementation> impl_; public: ~Book(); Book(); };

You could probably do

// hpp class Book { struct implementation; std::unique_ptr impl_; public: Book(); };

// cpp Book::Book(): impl_( new implementation, checked_delete<implementation> ) {}

Sorry if this is a silly question, but wouldn't this double the size of member variable impl_ (two pointers), just to save some typing? To me it doesn't look like a good tradeoff. I'm quietly following this thread, and I still don't get why std::unique_ptr is not good enough for heap-allocated pimpl.