Re: C++14: Papers
On Friday, May 24, 2013 1:02:08 AM UTC+1, =D6=F6 Tiib wrote:
On Thursday, 23 May 2013 21:34:27 UTC+3, Jorgen Grahn wrote:
On Tue, 2013-04-16, Sam wrote:
On 16/04/2013 12:21, James Kanze wrote:
(In the early days of C++, there were some who did try to
implement the "everything derives from Object" philosophy, with
boxing for the predefined types. Experience showed that it
wasn't a good idea. At all.)
And yet C# does it...
I must admit I don't really like it (along with the insistence that =
a
class only ever derives behaviour from one other) but I suspect they=
put
it in for the early versions, where the collections held Objects wit=
hout
any further specification.
I don't think there's anything inherently wrong with "most classes de=
rive
from object". Having an object superclass does have many advantages.
For those of us who have spent too much time with C++, what would
those advantages be? Based on what you write below, you seem to
describe a system where even logically unrelated classes derive from
object, but small/numerous objects may be exempted.
It means basically standardizing some common virtuals like 'equals',
'swap', 'clone', 'dump' and 'hash'. On most cases those could be made
to default to something that makes sense:
'T* T::clone() const {return new T(*this);}'
I'm afraid I don't see the logic here. Consider equals. In
C++, this is spelled operator==, and it is implemented over a
large number of object types (like int, double, etc.). Making
everything derive from Object, and have a virtual function
equals, however, doesn't make sense: it means that you can
compare the incomparable, and only get an error at runtime,
rather than from the compiler. Similar comments apply to all of
the functions you define: they don't make sense across unrelated
types (and in some cases, don't make sense at all).
Not to mention that most classes in (well written) C++ don't
have virtual functions.
The advantages (and disadvantages) of it can be similar to other
implicitly available things. There is number of such things in C++
(like copy constructor or assignment operator) already. Sometimes these
are helpful.
Things like copy construction and assignment were originally
only present for reasons of C compatibility.
--
James