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	2017-02-06 01:08 +0100
Organization	Aioe.org NNTP Server
Message-ID	<o78eqa$1omj$1@gioia.aioe.org> (permalink)
References	(2 earlier) <cwvdA.547229$AS2.194354@fx32.am4> <o57ijl$e39$1@dont-email.me> <dlLdA.831942$7m2.231803@fx37.am4> <o583e1$pjv$1@dont-email.me> <78OdA.1094575$zq4.804012@fx41.am4>

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On 01/12/2017 05:27 PM, JiiPee wrote:
> On 12/01/2017 14:23, David Brown wrote:
>> The reason you make the function return 0 on an empty set is so that
>> when a user writes this :
>>
>>     int x = average(set);
>>     printf("The average is %i\n, x);
>>
>> and "set" happens to be empty, then they will get the output "The
>> average is 0\n", rather than "Launching nasal daemons...\n".
>
>
> I see. But in this case I would prefer to use NaN or max_double so the
> user would see there is something wrong going on. Because 0 return looks
> like a success, but getting max_double would surely be noticed.
>
I believe you got exactly the point here, except that personally I would 
not like NaN - INF or max_double even less.
I would indeed go for the exception.

Returning a valid value (0) would likely result in the containing 
program to silently give some result which is not correct for the input 
data, which in my opinion is a Bad Thing.

Returning NaN would silently allow the program to complete with a NaN 
result, which would inform the user that invalid data was provided, but 
no more than that.

The exception is indeed meant to provide feedback that invalid data was 
provided /and/ what was wrong about it.

The above applies to the average() case, but more in general with 
floating point math division by zero can quite often be prevented by 
proper rearrangement of expressions and/or taking advantage of INF 
processing (NaN remains quite intractable though).
It may be worth noting that the average() calculation is not entirely 
floating point math - your denominator is an integer, which by no 
coincidence results in the situation to need to be handled as an error.

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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