Re: class wide iterable (and indexable)

[George Shapovalov <gshapovalov@gmail.com>]

Just on a small specifics here.

On Sunday, January 6, 2019 at 9:18:09 PM UTC+1, Dmitry A. Kazakov wrote:
> You override getter and/or setter. Whatever representation of inherited 
> bases stay unless overridden as a whole. The similar approach is used 
> for discriminants: either extension or overhaul. (The latter case may 
> not be limited, it must be strictly by-value)
So, out of 3 variants, you select the first one - to keep all things around and accumulate as you go, which *is* the safest, and probably the most sensible, way to do it. But this will not fly universally - what about situations where you have billions of copies of your record (all with different data). Wasting even small amounts per entry (and as stuff accumulates over years, that waste may become the majority of space taken) is a big no-no for some scenarios. So, for a "universal language" you must have a provision of data layout control (which Ada has) extended to such situations. Which means a more complex field handling. Which, in turn, leads either to exposing this to developers, thus augmenting abuse and insanity, or a really tricky and complex "garbage collection" working on dynamic type hierarchies. I am afraid there is no easy solution to that. And that compromise of treating "data" and "code" separately seems an acceptable tradeoff (even if yes, mathematically, it is possible to handle them in a universal way)..

But then it is true, with discriminants it is already violated. So I guess treating data the same way is the next natural step. Oh well, most developers will either be too scared to use that or will do nonsemsical things without proper understanding, leading to failed software and more possibilities for the rest of us to do things properly :).