Re: [boost] Interest in boost.deepcopy

Subject: Re: [boost] Interest in boost.deepcopy
From: David A. Greene (greened_at_[hidden])
Date: 2011-11-02 14:49:45

Dave Abrahams <dave_at_[hidden]> writes:

> on Mon Oct 24 2011, Allan Johns <allan.johns-AT-drdstudios.com> wrote:
>
>> Just gauging initial interest in a boost.deepcopy library
>
> <pet peeve alert>
>
> Sorry to slam this idea out of the gate, but the whole notion of a
> "deep copy" is broken and wrong (in my humble opinion).  When you say
> you're going to "deep copy" an object it shows you don't understand
> the boundaries of that object's value.  The object's value is copied
> by its copy constructor, and compared by its operator== (assuming it
> has one).  If your "deep copy" extends beyond the boundaries of the
> value, there's no way of knowing how far it should extend.

Fascinating discussion.  I'm curious about your statement here.  Do you
object to "deep copy" as implemented in a copy constructor or the notion
of "deep copy" of some aggregate data structure in general?

For example, I have often needed to clone some branch of a tree data
structure where nodes contain pointers to other nodes.  For me this is
in the context of a compiler and subtree cloning is a convenient way to
perform code duplication.  In the past I have implemented a virtual
clone() member for each kind of tree node in order to get polymorphic
behavior.  clone() clones child nodes and all that.

If your objection covers cases like the above, I am very interested in
alternative solutions.

Thanks!

                         -Dave