Furthermore look at your example. You offer 4 basic geometric types. But would you even really want to model them with an isa arrangement? I don't know about you, but when I think of modelling a square, most of the implementations that I would start with don't turn into good implementations of a parallelogram or rhombus. Unless, of course, I started knowing that I wanted parallelograms...
Yes, I want to model them in an isa arrangement. I wasn't thinking about "modelling" a square. I was thinking about a property system. A square has all the properties of a rectangle. A square has all the properties of a rhombus. Both the rectangle and the rhombus have all the properties of a parallelogram. What is more natural than multiple inheritance to express these facts? See also my response to flying moose.
Therefore I'm inclined towards merlyn's view. If you can solve your problem using single inheritance, do so.
While I agree with the latter, I don't think that's what Merlyn said. What he said was:
If the answer to a question is "multiple inheritance", you've probably asked the wrong question.
which to me means "never use multiple inheritance".

And when you learn another language, you can design the same way secure in the knowledge that single inheritance always is present, and its behaviour doesn't tend to change that much between languages so you have less relearning to do.
That I find a weak argument. I'm not shying away from hashes because normal arrays are always present in other languages and hashes may not. Besides, there are languages that don't have support for even single inheritance (for the mere fact they don't have native OO support).

Abigail

In reply to Re: inheritance and object creation by Abigail-II
in thread inheritance and object creation by knew

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