Re: Avoiding copying of an object

From:

=?ISO-8859-1?Q?Daniel_Kr=FCgler?= <daniel.kruegler@googlemail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Tue, 28 Sep 2010 03:22:25 CST

Message-ID:

<b2d1b1b9-e62c-4543-a066-5ff5d492028e@p26g2000yqb.googlegroups.com>

On 27 Sep., 04:50, Adam Markiewicz <amgo...@gmail.com> wrote:

I'm designing a container class similar to those in STL. It is implemented
as a template with two parameters: contained type and an allocator.

template <typename Type, typename Allocator>
class FixedArray
{
...

}

Now, to write a function that takes FixedArray as a param to support
different allocators I would need (example):

template <typename Allocator>
float average(const FixedArray<float, Allocator>& array);

However array is const, so Allocator wouldn't be needed at all. Is would be
much simpler to write:

float average(const FixedArray<float>& array);

This syntax can be provided by specifying a suitable copy constructor, but I
want to avoid unnecessary copying overhead. Is there some other clean
solution to this problem?

You could partition FixedArray in a base class
which depends solely on T and a derived class
that adds the allocator dependency.

The name FixedArray irritates me: What is fix?
Where is the allocator needed? If you need it
for construction (and possibly assignment)
purposes only, you should consider to remove the
allocator dependency from FixedArray. In some
sense std::function is similar to such a design.

HTH & Greetings from Bremen

Daniel Kr?gler

--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]