Re: Nice Interfaces == Traits ?

>>I'm not sure the term "trait" is well known outside of the circle of 
>>language researchers (like you ;-), nor that it conveys an evident 
>>meaning. So most people would have to learn what a trait is and to
>>keep remembering using it instead of interface.
>>    
>>
>
>I agree - they'd know straight away that this is a new thing they need
>to learn about, rather than the ubiquitous specification-only thing.
>  
>
Only you do not need to learn anything to start using interfaces in 
Nice. It just happens that you can do more things with them than you can 
with Java interfaces.

BTW, this shows that traits are not the same as Nice interfaces, since 
if I recall right they cannot be part of a hierarchy.

>>On the other hand, it is not hard to explain that among the
>>advantages of multi-methods (declaring new methods on existing
>>classes, specializing on all arguments) there is also the ability to
>>implement a method for an interface. Simple, no?
>>    
>>
>
>I'm not sure multimethods are well known outside of the circle of
>language researchers ;-)
>  
>
Sure. So we need to document them, including how they can be specialized 
on interfaces.

>>I would find it awkward to change the name of interfaces just because
>>of this fact, because it has nothing to do with interfaces
>>themselves, it has to do with the flexibility of multi-methods.
>>    
>>
>
>The idee fixe is that interfaces are only declaration.
>  
>
I don't think you define something by what it is not. That's actually 
quite contrary the idea of OO, since you always keep the option to add 
features (in subclasses). For instance, you cannot say that a Point is 
something that does not have a color, since it might actually be a 
ColoredPoint.

So I think the defining aspect of interfaces is that one can implement 
multiply from them. It happens that in Java one cannot implement methods 
inside interfaces, but that's a limitation (which is there to simplify 
the implementation of multiple implementation), not a feature.

>That's a helpful analogy. Many of the comments I make about Nice
>probably have some grounding in a guess about how much we'll have to do
>when making code changes - because so much more effort goes into making
>code changes then into designing a hierarchy anew. 
>  
>
That's a valid concern.

Daniel



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