Re: Best way to handle mathematical divide-by-zero case

From	Manfred <mx2927@gmail.com>
Newsgroups	comp.lang.c++
Subject	Re: Best way to handle mathematical divide-by-zero case
Date	2017-02-07 00:58 +0100
Organization	Aioe.org NNTP Server
Message-ID	<o7b2ih$1mvi$1@gioia.aioe.org> (permalink)
References	(6 earlier) <78OdA.1094575$zq4.804012@fx41.am4> <o78eqa$1omj$1@gioia.aioe.org> <UAPlA.210290$sc6.108277@fx25.am4> <o79rp3$1jh0$1@gioia.aioe.org> <_I6mA.570101$Zf5.376281@fx41.am4>

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On 02/06/2017 11:25 PM, JiiPee wrote:
> On 06/02/2017 12:56, Manfred wrote:
>> On 2/6/2017 1:39 AM, JiiPee wrote:
>>> On 06/02/2017 00:08, Manfred wrote:
>>>> I would indeed go for the exception.
>>>
>>>
>>> But Bjarne seems to be against exception in this kind of situation...
>>>
>> I don't recall when/where he may have said that, I would be curious;
>> could you be more specific if you like?
>
> http://stackoverflow.com/questions/6121623/catching-exception-divide-by-zero
>
>
> Stroustrup says, in "The Design and Evolution of C++" (Addison Wesley,
> 1994), "low-level events, such as arithmetic overflows and divide by
> zero, are assumed to be handled by a dedicated lower-level mechanism
> rather than by exceptions. This enables C++ to match the behaviour of
> other languages when it comes to arithmetic. It also avoids the problems
> that occur on heavily pipelined architectures where events such as
> divide by zero are asynchronous."`
>
Thanks for the quote.
I may have two comments about this:

1) Appearently Bjarne is referring here to exceptions thrown by the 
language itself (or the standard library), and he explains why they 
choose not to have the language throw a division-by-zero exception - in 
which the argument to match the behaviour of other languages (including 
C) is a strong one.
In the average example() I would explicitly throw an exception if the 
set is empty, I would not execute the division by zero, or anyway assume 
that the division itsels throws an exception.

2) In the general case of floating point arithmetic division by zero 
would have some real-valued denominator expression that can evaluate to 
zero or any value arbitrarily close to it. In the average() example the 
denominator is an integer value, and this is a relevant difference.

As I wrote earlier, when there is a real-valued denominator that can 
evaluate to zero or any value close to it, quite often (expecially when 
the expression models a physical process) if you happen to have the 
expression evaluate to 0/0 (which would yield a NaN) you can in fact 
refactor the expression so as to have a well defined form over your 
problem domain.
If you happen to get nonzero/0, you may either choose different 
variables, or rely on the processor or math library handling of +/-INF 
if this suits your problem.
This is to say that with real-valued floating point arithmetic, you have 
significant alternatives to handle (or prevent) division by zero before 
you treat it as an error condition. Obviously all of this must be 
studied in the specifics of the problem at hand.
In my experience division by zero is not the hardest part of floating 
point arithmetic. Actually much easier than its finite precision and 
rounding errors, which would result e.g. in DBL_EPSILON to be returned 
where a zero was expected. This can be much trickier.

Thread

Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-11 18:17 +0000
  Re: Best way to handle mathematical divide-by-zero case "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2017-01-11 20:00 +0100
    Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-11 19:16 +0000
      Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-12 10:36 +0100
        Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 13:16 +0000
          Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-12 15:23 +0100
            Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 16:13 +0000
              Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-12 17:35 +0100
            Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 16:27 +0000
              Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-12 17:37 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 16:44 +0000
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 16:46 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-13 12:06 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-13 11:36 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-13 13:12 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-13 13:11 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-13 15:23 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-13 14:57 +0000
                Re: Best way to handle mathematical divide-by-zero case "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-13 17:35 -0800
                Re: Best way to handle mathematical divide-by-zero case Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-13 20:25 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-14 18:08 +0100
                Re: Best way to handle mathematical divide-by-zero case Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-14 20:30 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-15 00:16 +0100
                Re: Best way to handle mathematical divide-by-zero case Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-15 00:34 +0000
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-15 01:01 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-15 16:57 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-15 17:17 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-15 19:13 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 16:48 +0000
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 16:51 +0000
              Re: Best way to handle mathematical divide-by-zero case Manfred <mx2927@gmail.com> - 2017-02-06 01:08 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-02-06 00:39 +0000
                Re: Best way to handle mathematical divide-by-zero case Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2017-02-06 00:50 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-02-06 02:01 +0100
                Re: Best way to handle mathematical divide-by-zero case Manfred <noname@invalid.add> - 2017-02-06 13:56 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-02-06 22:25 +0000
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-02-06 22:26 +0000
                Re: Best way to handle mathematical divide-by-zero case Robert Wessel <robertwessel2@yahoo.com> - 2017-02-06 16:46 -0600
                Re: Best way to handle mathematical divide-by-zero case Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2017-02-06 23:49 +0000
                Re: Best way to handle mathematical divide-by-zero case scott@slp53.sl.home (Scott Lurndal) - 2017-02-07 13:24 +0000
                Re: Best way to handle mathematical divide-by-zero case Manfred <mx2927@gmail.com> - 2017-02-07 00:58 +0100
                Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-02-07 00:43 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-02-07 09:22 +0100
                Re: Best way to handle mathematical divide-by-zero case Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-07 14:06 +0000
                Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-02-07 15:58 +0100
                Re: Best way to handle mathematical divide-by-zero case Öö Tiib <ootiib@hot.ee> - 2017-02-07 01:00 -0800
                Re: Best way to handle mathematical divide-by-zero case Manfred <noname@invalid.add> - 2017-02-07 15:31 +0100
                Re: Best way to handle mathematical divide-by-zero case scott@slp53.sl.home (Scott Lurndal) - 2017-02-07 13:22 +0000
        Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 13:20 +0000
          Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-12 15:28 +0100
            Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 15:40 +0000
              Re: Best way to handle mathematical divide-by-zero case David Brown <david.brown@hesbynett.no> - 2017-01-12 16:52 +0100
    Re: Best way to handle mathematical divide-by-zero case Wouter van Ooijen <wouter@voti.nl> - 2017-01-11 23:20 +0100
  Re: Best way to handle mathematical divide-by-zero case Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2017-01-11 21:43 +0000
    Re: Best way to handle mathematical divide-by-zero case Gareth Owen <gwowen@gmail.com> - 2017-01-12 19:12 +0000
  Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 00:07 +0000
  Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 00:12 +0000
  Re: Best way to handle mathematical divide-by-zero case Real Troll <real.troll@trolls.com> - 2017-01-12 12:55 -0400
    Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-12 16:53 +0000
  Re: Best way to handle mathematical divide-by-zero case Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2017-01-12 19:10 +0000
    Re: Best way to handle mathematical divide-by-zero case Gareth Owen <gwowen@gmail.com> - 2017-01-12 19:17 +0000
  Re: Best way to handle mathematical divide-by-zero case "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-13 15:34 -0800
    Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-14 00:14 +0000
      Re: Best way to handle mathematical divide-by-zero case "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-13 16:56 -0800
        Re: Best way to handle mathematical divide-by-zero case "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-13 17:46 -0800
        Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-14 01:51 +0000
          Re: Best way to handle mathematical divide-by-zero case "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-13 18:09 -0800
    Re: Best way to handle mathematical divide-by-zero case Gareth Owen <gwowen@gmail.com> - 2017-01-14 11:21 +0000
      Re: Best way to handle mathematical divide-by-zero case "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-14 12:45 -0800
        Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-01-14 21:02 +0000
          Re: Best way to handle mathematical divide-by-zero case "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-14 13:47 -0800
        Re: Best way to handle mathematical divide-by-zero case "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-14 13:03 -0800
  Re: Best way to handle mathematical divide-by-zero case "J. Clarke" <j.clarke.873638@gmail.com> - 2017-02-04 07:56 -0500
  Re: Best way to handle mathematical divide-by-zero case Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-02-05 10:21 +0000
    Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-02-05 13:33 +0000
      Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-02-06 07:33 +0000
    Re: Best way to handle mathematical divide-by-zero case JiiPee <no@notvalid.com> - 2017-02-05 13:34 +0000
      Re: Best way to handle mathematical divide-by-zero case Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-02-05 18:51 +0000

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