RE: [boost] Re: Conversion from auto_ptr to scoped_ptr?

From: Bjorn.Karlsson_at_[hidden]
Date: 2002-06-17 16:57:44

> From: Markus Schöpflin [mailto:markus.schoepflin_at_[hidden]]
[snip]
> Hmm, I did some further thinking on this and I simply can't see the
> difference between the current shared_ptr, which offers a 
> conversion from
> auto_ptr and my suggestion for scoped_ptr.
> 
> Could you enlighten me, Peter? Or anybody else?
> 

I'd argue that introducing a dependency to std::auto_ptr is not in the best
interest of scoped_ptr. It seems to me that scoped_ptr differs from
shared_ptr in design intent - scoped_ptr should know and require as little
as possible (but no less), whereas shared_ptr takes pride in being smart.

There are two idioms that can be used to approximate scoped_ptr in the
scenario where an auto_ptr is returned from a function:
0) Declare the auto_ptr const. This comes very close to the behavior of
scoped_ptr, with the exception that you can reset the scoped_ptr, but not
the auto_ptr.
1) Use solution 0 together with scope (pun intended): { const
std::auto_ptr... }. This takes care of most cases where the pointee must be
deleted at a certain location in the code.

Armed with these tools, the most compelling argument that remains for adding
the conversion from auto_ptr to scoped_ptr is stating the intent of code
more clearly; but does the added value really outweigh the cost of the added
dependency?

Bjorn