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GCC 4.6.0 releasedGCC 4.6.0 releasedPosted Apr 5, 2011 22:43 UTC (Tue) by HelloWorld (guest, #56129)In reply to: GCC 4.6.0 released by cmccabe Parent article: GCC 4.6.0 released
Firstly, this is a general statement about inheritance and has little to do specifically with multiple inheritance. Secondly, if we assume the GoF to be right, then Java did it just as wrongly as C++, as it still allows inheritance.
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GCC 4.6.0 released Posted Apr 5, 2011 23:24 UTC (Tue) by cmccabe (guest, #60281) [Link]
My main point is that using inheritance for code reuse is bad.
Using inheritance to implement runtime polymorphism is still ok.
So Java interface classes and C++ abstract base classes are ok in my book. Mixins are bad, in my opinion.
I do like the way Golang handles runtime polymorphism more than the way C++ or Java do it, but you can only do it that way if you're using Go. :)
GCC 4.6.0 released Posted Apr 7, 2011 16:42 UTC (Thu) by daglwn (subscriber, #65432) [Link]
Mixins do not have to implement anything. Again, you're artificially restricting what's possible. It's sometimes convenient to use mixins to convey relationships among types. I have a mother and a father. My mother has a mother and a father. So does my father. That means my maternal-side cousin and I have grandparents in common and my paternal-side cousin and I also have grandparents in common, but a different set.
In more concrete terms, an add expression is a binary operator. So is a subtract expression. Both are also associative, but only one is commutative. That's a useful thing to express in class hierarchies and using mixins is a great way to do it.
GCC 4.6.0 released Posted Apr 8, 2011 17:57 UTC (Fri) by cmccabe (guest, #60281) [Link]
from Wikipedia:
> In object-oriented programming languages, a mixin is a class that provides
So it's not about relationships between types. It is about code reuse.
Bruce Eckel suggests a way of implementing mixins in C++ using templates:
http://www.artima.com/weblogs/viewpost.jsp?thread=132988
I would suggest yet another: private inheritance.
GCC 4.6.0 released Posted Apr 8, 2011 18:35 UTC (Fri) by daglwn (subscriber, #65432) [Link]
I've used CRTP as well and find it useful. I also find mixins as relationship useful. I my mind, inheritance is about relationships. For functionality, I would agree with GoF and you that composition is generally a better path. I very rarely use private inheritance. I honestly can't think of a situation where I've found it absolutely necessary.
But in any case, I think the discussion leads us to a place where general MI is useful, even with the pitfalls. Pointers in C have a similar usefulness/pitfall tradeoff. I like the fact the C++ is flexible like this. I wish it were more flexible than it is! :)
GCC 4.6.0 released Posted Apr 11, 2011 0:30 UTC (Mon) by cmccabe (guest, #60281) [Link]
Well, as I said before, I think being able to inherit from multiple (fully) abstract base classes is useful. I have never found a good use for inheriting from multiple non-abstract base classes. I guess we'll have to agree to disagree.
Anyway, language design is an endless process. It really comes down to who what languages are most successful in the marketplace, and in the open source world. My philosophy is to use the right tool for the job.
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