Re: class wide iterable (and indexable)

[George Shapovalov <gshapovalov@gmail.com>]

On Sunday, January 6, 2019 at 1:45:09 PM UTC+1, Dmitry A. Kazakov wrote:
> Yep, Max Planck:
[..]
Ah, yes indeed, thank you for the specifics, it was a while ago that I last had to recall that :).

> Yes. Interface is an abstract tagged type, nothing more except for a 
> silly constraint not to provide anything functional.
Ah, so you mean that if the "stupid nonfunctionality constraint" is removed then there is no need to have an extra reserved word? I see. But there are reasons beyond that. One would be readability and consistence with generally accepted (by now) OOP composition paradigm. Another, and perhaps even more essential is that that non-functionality is two-fold: 
1. provision of inheritable primitives, which is the really lacking feature IMHO (and evidently in opinion of many other people),  and
2. provision of data entries.

The 2nd one, while useful in some situations, can usually be worked around with proper type layout. In fact such prohibition forces to think type layout through up-front often saving much grief later. Moreover, lookup collision resolution rules are very often different for data and methods, quickly causing mess of things. So I think, at least on this one there is a good reason to keep it as is. As such, reserved word "interface" would stand for an abstract type without actual data but with inheritable primitives. Not only this would satisfy many (more) opponents, but it would provide a more complete set coverage of "problem decomposition scenarios"..

George