Re: Problem in "X (1).Re := X (1).Re + 1"

["Randy Brukardt" <randy@rrsoftware.com>]

"ytomino" <aghia05@gmail.com> wrote in message 
news:8861140.211.1336552896666.JavaMail.geo-discussion-forums@pbcrz9...
> On Wednesday, May 9, 2012 7:29:14 AM UTC+9, Randy Brukardt wrote:
>>
>> (Note that a copy-on-write implementation is not a good idea for the
>> standard containers for other reasons as well,
>
>> the main one being that the usual uses don't create many copies,
>
> Really?
> Ada.Containers.Vectors have some "&" operators.
> Many copies may be created when doing X & A & B & C...

Sure, the containers have some operations where this implementation would be 
a benefit. But I would guess that those operations would be used very rarely 
(if ever), so optimizing for them would be a mistake.

I think this is similar to the usage of the operations in 
Ada.Strings.Unbounded. There are many operations defined in that package, 
but most code I've seen only uses a handful of those operations. Optimizing 
for the other operations is wasted effort.

That's way I said it might make sense to use this implementation in your own 
container package, because your usage patterns might be far from typical. 
(There cannot be a one-size-really-fits-all implementation.)

                                  Randy.