Re: ADA Popularity Discussion Request

["Alexander E. Kopilovich" <aek@VB1162.spb.edu>]

Richard Riehle wrote:

> There are a few simple underlying ideas in the language. One
> of them is type safety, and that has never been beyond the
> comprehension of any programmer.   The idea that seems to
> have been difficult to grasp, even by many who consider themselves
> sophisticated software developers, is the separation of scope
> and visibility.   Chapter Eight of the ALRM is rarely read by
> anyone, it seems.
Certainly so. It was said many times (here in c.l.a. and elsewhere) by the
most authoritative Ada experts that ALRM is NOT intended for use by regular
software developer but it is for Ada experts (mostly by Ada compiler writers).
And in many places it is indeed difficult to read - because information is not
strictly localised - you can never be sure that there is no important bit of
related information somewhere, in some distant place of the ALRM.

Actually, a reader of ALRM can't be sure of any broad statement if s/he did
not study the ALRM comprehensively - and naturally, almost no one except
professional Ada experts can afford that.

The idea of type safety is easy because it is an abstract idea, Ada did not
invent (or even modify) but just employs it. In other words, this idea is
easy for a programmer because it comes not from ALRM, and actually not from
Ada -;) .

But the separation of visibility and scope, which you mentioned, never was
formulated as a clear abstract idea, it is closely associated with Ada - and
therefore there is no affordable way to understand it properly as a separate
idea.

> The benefits of the visibility rules needs to be given emphasis.  Those
> rules are among the most powerful benefits of Ada, even though
> some programmers continue to see them as a nuisance.
Then what prevents you (or someone else) from explaining this idea - first
in some abstract form and then showing how this abstract idea is employed in
Ada language?




Alexander Kopilovich                      aek@vib.usr.pu.ru
Saint-Petersburg
Russia