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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Teaching C/C++ from Ada perspective?
Date: Thu, 5 Jul 2018 13:31:16 -0500
Organization: JSA Research & Innovation
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"Maciej Sobczak" <see.my.homepage@gmail.com> wrote in message 
news:559657f8-bbf4-4a70-9449-f85bc98d6c6b@googlegroups.com...
...
>Yet, the trivial update of P (like adding whitespace, which again has no
>semantic meaning whatsoever) forces the recompilation of Test (with
>GNAT). Actually, it forces the recompilation of everything. Why?
>
>There go your "semantic" devices for programming in the large. Sorry,
>but even though I do understand the intent, I don't see it in practice.

You need to use a "better" Ada compiler. GNAT /= Ada!!! In particular, the 
Rational environment from back in the day used incremental compilation 
techniques such that a modification to P would only cause recompilation of 
entities that actually depended on declarations in P. So your example of a 
whitespace change would cause no recompilation at all (even of P).

One could make an argument that the "market" finds this entire issue 
irrelevant, since it seems to gravitate to C++ and Ada compilers like GNAT 
rather than ones like Rational. (For Janus/Ada, recompilation is fast enough 
that there's little value to trying to avoid recompilation in such cases --  
it would be more work than it would gain time. Perhaps it would matter more 
in multi-million line codebases, but we don't have any such customers.)

                                                          Randy.