Addressing your example, in Ruby, the mixin Comparable is equivalent to the Eiffel one. You define <=> and the rest comes for free. I do not discount the power of doing that. Nor am I discounting the fact that with traits you could reduce the amount of code and clean other code up.

However I am saying that this power comes at a constant development cost in terms of figuring out what is happening, why, where and when. This is not something that is visible in the statistics that you quote. This is something that shows up gradually when someone is lost in code and wandering around saying, "Where did foobar() get defined again, and how do I get it again?" Or alternately when you are wandering around saying, "I have a foobar(), but it isn't what I expected it to be? Why not? And where is this coming from?"

Also if you go up to the link I had on mixins, you'll find that my opinion is somewhat finely nuanced. I don't think that mixins (or traits, or roles, or...) are Evil Incarnate. I just think that they impose a cost for their benefit, and the cost is one that needs to be carefully understood before deciding to splurge on their usage.

Programmers who know when to use them and (more importantly) when not to use them will find them nice and not very problematic. Programmers who don't know that (and most of those who clamour most loudly do not) get lots more rope. I guess that that fits with Perl's design philosophy (give em enough rope to hand themselves), but that doesn't mean that I shouldn't offer advice on how to avoid self-hanging.

In reply to Re: Re: Re: Re: Re: Re: inheritance and object creation by tilly
in thread inheritance and object creation by knew

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