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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Lower bounds of Strings
Date: Tue, 12 Jan 2021 02:19:24 -0600
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:rtc1vu$1cfj$1@gioia.aioe.org...
...
> Of course it will simplify everything. E.g. our beloved generics. Compare
>
>    generic
>       type I is (<>);
>       type E is private;
>       type A is array (I range <>) of E;
>
> with
>
>    generic
>       type A is new Root_Array_Type with private;

Surely, it simplifies it to uselessness. You haven't declared the index and 
component types here. And if they are implicit in Root_Array_Type, you've 
now run into the fundemental problem of interfaces: you need a generic or 
everything has to be related in order to use an interface.

For instance, you can't have a useful container interface because the 
interface has to somehow contain the element type. The only way to do that 
is to add additional generics (which is madness), or require all of the 
elements to be descendants of some root type (which is a different form of 
madness).

Interfaces aren't a free lunch, they just add complexity (or, at best, move 
it around). One has to look at the entire set of declarations needed, not 
just one use (it would be a sorry language feature indeed if you couldn't 
find any example that it simplified!).

                                       Randy.