From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!feeder.eternal-september.org!gandalf.srv.welterde.de!news.jacob-sparre.dk!loke.jacob-sparre.dk!pnx.dk!.POSTED!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Problems with SPARK 2015 and XMLAda
Date: Mon, 24 Aug 2015 16:32:43 -0500
Organization: JSA Research & Innovation
Message-ID: <mrg2hr$qtl$1@loke.gir.dk>
References: <e3de50ce-e994-4038-8160-13266aeb207e@googlegroups.com>
 <lymvxn112j.fsf@pushface.org>
 <6952b70d-a9bc-4d0a-beb5-1cd38d6a3318@googlegroups.com>
 <9d3dc132-4e1a-4e9c-bcd4-82a42a73745f@googlegroups.com>
 <mr5dnn$ce9$1@loke.gir.dk> <alpine.DEB.2.20.1508210804480.22981@debian>
 <puak04qc3k8o$.1epetyorakzeg$.dlg@40tude.net>
 <alpine.DEB.2.20.1508210948320.23241@debian>
NNTP-Posting-Host: rrsoftware.com
X-Trace: loke.gir.dk 1440451964 27573 24.196.82.226 (24 Aug 2015 21:32:44 GMT)
X-Complaints-To: news@jacob-sparre.dk
NNTP-Posting-Date: Mon, 24 Aug 2015 21:32:44 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-RFC2646: Format=Flowed; Original
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157
Xref: news.eternal-september.org comp.lang.ada:27597
Date: 2015-08-24T16:32:43-05:00
List-Id: <comp.lang.ada>

<Stefan.Lucks@uni-weimar.de> wrote in message 
news:alpine.DEB.2.20.1508210948320.23241@debian...
...
> I doubt this makes any observable difference. The legitimate examples for
> exceptions that "signal things that cannot be known at compile time" (as
> Randy wrote) are usually related to input-output operations.

You really should say "external environment" rather than I/O. Anything that 
the target OS (or hardware!) provides is in that category -- environment 
variables (what if some other program adds/deletes a variable?), command 
lines, memory management (allocating too much memory), clocks, GUI (what if 
the user of the program manually closes a window? That can happen at any 
time.)

Not all of these things are slow in the sense of external I/O devices. The 
difference between exceptions and error codes (particularly as keeping OS 
error codes task safe adds an expense) may be more significant.

(But clearly the main issues are readability, locality, and the requirement 
to handle them.)

                                 Randy.