Re: Public virtual harmful? (was Re: Testing Program Question)
On Feb 28, 4:38 pm, Jorgen Grahn <grahn+n...@snipabacken.se> wrote:
On Wed, 2010-02-17, James Kanze wrote:
On Feb 16, 11:49 am, "Leigh Johnston" <le...@i42.co.uk> wrote:
[...]
These are only "exceptions" to some stupid rule that
only a subset of the C++ community happen to agree with
including yourself.
The "subset" includes most of the experts. People like Herb
Sutter, for example.
I don't want to get involved in an old argument, but James,
where can I read more about the reasoning behind this? It was
a new opinion to me; I don't think I've come across it before.
The article which brought the idea into mainstream programming
is http://www.gotw.ca/publications/mill18.htm, by Herb Sutter.
(I'm not sure I agree with all of this article---in particular,
he refers to this as the template method pattern. While is does
have some superficial simiarity to the template method pattern,
the goals and the rational behind it are considerably
different.) The idea wasn't particularly new even then: I think
Nathan Meyrs was one of the early proponents (and I suspect that
his influence in the library group of the C++ standards
committee is why std::streambuf has no public virtual
functions), although I don't know what his exact motivations
were. I'd also heard of it as a means of implementing PbC from
somewhere else, although I believe I was one of the early
proponents of this point of view. At any rate, Herb Sutter's
article is a good introduction, even if he missuses a word or
two, and sometimes overstates the case.
I have some kind of dislike for run-time polymorphism in
general. Maybe this can help me understand *why* I dislike
it.
There's nothing wrong with run-time polymorphism, when it solves
the problem at hand. Like everything else, however, it's not a
silver bullet. It adds complexity, and if that complexity
doesn't buy you something more valuable in return, you shouldn't
introduce it.
--
James Kanze