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

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.lang.c++
Subject	Re: Best way to handle mathematical divide-by-zero case
Date	2017-02-07 09:22 +0100
Organization	A noiseless patient Spider
Message-ID	<o7c00v$qke$1@dont-email.me> (permalink)
References	(8 earlier) <UAPlA.210290$sc6.108277@fx25.am4> <o79rp3$1jh0$1@gioia.aioe.org> <_I6mA.570101$Zf5.376281@fx41.am4> <o7b2ih$1mvi$1@gioia.aioe.org> <PK8mA.722159$Ww5.170172@fx42.am4>

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On 07/02/17 01:43, JiiPee wrote:
> On 06/02/2017 23:58, Manfred wrote:
>> 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. 
> 
> 
> what if the average is calculated 10 million times per second? would you
> still ldo the check eatch time?
> 
> But isnt it this a similar issue to vectors v.at(2) against v[2]?
> 

Do you prefer correct code, or code that is a fraction of a percent
faster but wrong?

It is really quite simple, and I cannot understand why you are taking so
long to get the hang of it.

Let me give you the /one/ rule that actually matters:

* Do not divide by zero - it is a mistake in the code. *

OK?

Now you have that as a rule, you can decide the best way to be sure that
the rule is not broken.  That will depend on the circumstances - what
code you have, who is going to call the code, who might make the mistake
of threatening a division by zero, and what you can do about it.
Options include everything from ignoring it (because if some moron calls
your function with an empty set, it is /their/ fault - and you don't
want to slow down the code for competent users), returning fixed values,
throwing an exception, up to automatically sending out an email to the
developers with a deviation report.

The same applies to /all/ other undefined behaviour in the code (such as
accessing an array out of bounds) and all other kinds of errors.  Your
target is to avoid them happening.  If you think an error /might/
happen, then you find ways to detect the situation and deal with it as
best you can.

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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