On Sep 15, 4:23 pm, Erik Wikström <Erik-wikst...@telia.com> wrote:
> On 2007-09-15 15:09, terminator wrote:
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> > On Sep 11, 11:03 pm, werasm <wer...@gmail.com> wrote:
> >> terminator wrote:
> >> > I said huge because a container contains data spatered all over the
> >> > heap and when it comes to copy(instead of reference) ,then it does not
> >> > matter if the data is stored in a contigeous portion of memory or
> >> > segmented into peices on different corners of memory.the actual size
> >> > of a container is often much larger than its own data structure(one or
> >> > two pointers and intrinsic values as well as the vtable in runtime
> >> > polymorphic ones).
>
> >> In that case I don't see how it contributes to your argument of using
> >> a pointer to the container instead of the actual container, if I
> >> understand you correctly, as whether one uses a pointer to
> >> a container, or the container itself, you always going to use the
> >> heap, and in the case of a pointer to the container, slightly more
> >> than in the other case, as now the pointer members are also on
> >> the heap.
>
> > only dynamic objects are placed on heap not pointers to objects,also
> > pointers can simply point to some stack variable in the presenet
> > thread as well.
> > The contribution? Very obvious!!! Copying containers is generally both
> > memory and runtime consuming and should be avoided whenever
> > possible ,and the simplest way is to use ref/ptr semantics.
>
> >> As far as inside a container is concerned, it depends on the type
> >> T. Typically, if I want to prevent copying, I use either pointers,
> >> or even a pointer_container aka. boost::ptr_vector. If copying of
> >> the container does not happen often, and T has the relevant
> >> members required, then I use T (by value).
>
> > I am talking about the container itself, not the elements.If one
> > address/refrences a container no element copy is performed but copying
> > a container is a nightmare sometimes,eventhough elements are pointers.
>
> Yes, what you say is true, but it is a question of semantics. For some
> types the container should be copied for some it should not, you should
> only use pointers where the containers are shared (and perhaps not even
> then, you can use "smart" containers instead).

???what is that one?somewhat smart ptr?

thanks,
FM.