division of objects into classes and structures is bad

Weed resume755 at mail.ru
Mon Dec 29 02:15:10 PST 2008


Denis Koroskin пишет:

>>  80490eb:       8d 85 6c fe ff ff       lea    -0x194(%ebp),%eax
>>  80490f1:       50                      push   %eax
>>  80490f2:       8d 85 2c fb ff ff       lea    -0x4d4(%ebp),%eax
>>  80490f8:       e8 67 ff ff ff          *call   8049064*
>>  80490fd:       e8 62 ff ff ff          *call   8049064*
>>     return c2.i;
>>  8049102:       8b 85 cc fc ff ff       mov    -0x334(%ebp),%eax
>> ...
>>
>>
>> (in 80490f8 and 80490fd simply two calls successively)
>>
>> If structures and classes were same that excellent optimization in any
>> case would turn out
> 
> If that's your use case, then your should seriosly reconsider using
> struct instead of class for your objects.

Classes always give such overhead if them to use in such quality. For
example, classes basically cannot be used as any mathematical objects
using overload of arithmetics. But also not only arithmetics, it it is
simple as a good example.

> Alternatively, you can use +=
> instead.

Here yes, but if I add classes of different types? Then not to escape
any more from creation of the temporary object in the heap.

> Other than that, this is not a convincing argument.
> 
> Reading many of your posts I came to a conclusion that you are
> shortsighted and too crazy about performance. What you care about is a
> premature optimization, which is a root of all the evil. You should
> ensure that your programm is complete and correct, first and *then*
> start doing profiling and optimizations.

The program is already ready. It entirely consists of the various
mathematics. Approximately %30 times of performance are spent for
similar superfluous work. On C++ the program will work on %30 faster (I
hope :)) and on D I am will turn out to do nothing with it.


> 
> Going back to the topic, dividing user types into two cathegories
> (structs and classes) is considered modern and right.

I do not accept such argument:)

> Some languages
> lack structs support at all (e.g. Java), but structs are too useful for
> optimization and language interoperation to drop them in a systems
> programming language. Some lack classes and try doing everything with
> structs (C). D takes the best of both worlds.

Probably I have not understood something, but I do not suggest to refuse
structures in general. I suggest to allow to create classes on a stack
as it is made in C++. That is actually to make structures and classes
same, than they and are, for example, in C++.

In the initial message I have shown that for perfomance important that
the class could be transferred and on value. And it not artful premature
optimisation - objects on value always so are transferred, all
programmers know it and use when do not wish to allocate a place in a
heap, that is usually always when the object will live in {}.

Besides, a class in a stack it is normal - keyword addition "scope" for
classes too speaks about it.

Rigidly having divided classes and structures D deprives of the
programmer of some possibilities which give it C++-like languages. I
consider that such languages should give all possibilities which allows
CPU but hiding concrete architecture, otherwise I would choose less
difficult in use language.



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