Re: why don't the STL containers all inherit from a common container class to allow generic iteration?

From:

peter koch larsen <peter.koch.larsen@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Tue, 8 Dec 2009 20:20:35 CST

Message-ID:

<831f5cff-286e-42cd-8a2d-1a62be7d3749@z41g2000yqz.googlegroups.com>

On 7 Dec., 20:52, Andrew <marlow.and...@googlemail.com> wrote:

Subject says it all really. I have been in Javaland for a while where
you do have this capability. I am aware of Meyers Effective STL item 2
("beware of the illusion of container-independent code") but I don't
think item 2 applies when all you want to do is iterate over a
container. This is the simple case that people want to do most of the
time (IMHO). Of course if you want to do something else like reverse
iterate etc then with C++ you can. But it does seem mysterious to me
why it is more awkward to do a generic iteration for the most common
case.

I realise that in the upcoming standard the use of auto to declare the
iterator will make it slightly easier.

So what is it you want to do that you can't do with a simple template-
function (that is probably already made for you and can be found in
e.g. <algorithm>)?
Requiring iterators to have virtual functions would not only increase
the memory- and cpu-footprint of your program; it would also prohibit
using ordinary pointers as iterators and require the elements
themselves to be derived from a common baseclass. If not, how would
you dereference an iterator?

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