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From: "G.B." <bauhaus@futureapps.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Operating System differences and Ada OS independent programming
Date: Wed, 23 Mar 2016 16:08:17 +0100
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Date: 2016-03-23T16:08:17+01:00
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On 23.03.16 09:38, Dmitry A. Kazakov wrote:
> For anything impossible under the given OS Use_Error is propagated.

In some cases a substitution mechanism might work:
If "E:\" is covered by some "multiple roots" type,
and the filesystem is Unix style, the Use_Error
could be staged, and conditional. The run-time
support that establishes the type's associated behavior
(or path mapping) would be configurable. The
programmer specifies a mapping mechanism from the
"multiple roots" object representing "E:\" to some
other "multiple roots" object that can play the
same role on his or her system.  Provided, maybe,
that the original object did not specifically use
"root-ness", which could be reflected in some constant
property preventing the above mentioned mapping.

So, then, Use_Error would be raised either

- if the mapping could not be performed because the
   target object would not represent "root-ness",

- or if no mapping was provided by the programmer,

- or if the mapping "tampers with file systems",

- or if the run-time system does not support mapping.