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

From	Manfred <noname@invalid.add>
Newsgroups	comp.lang.c++
Subject	Re: Best way to handle mathematical divide-by-zero case
Date	2017-02-07 15:31 +0100
Organization	Aioe.org NNTP Server
Message-ID	<o7clo4$1ssh$1@gioia.aioe.org> (permalink)
References	(8 earlier) <UAPlA.210290$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 2/7/2017 1:43 AM, 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?
Yes, unless in the program by some means it can be guaranteed that the 
set can /never/ be empty.
As others have already replied, ensuring a correct result is more 
important than saving a few (or many) clock cycles: if you want to save 
processing time, you have to do so in such a way that still guarantees 
correct results.

>
> But isnt it this a similar issue to vectors v.at(2) against v[2]?
>
It is a different context (out of range is not division by zero). Anyway 
for vector elements the designers of the language decided to provide two 
access methods, only one of which guarantees range checking. Obviously 
this implies that if you want to use the [] form (unchecked) you /need/ 
to ensure that the vector will /never/ be accessed out of range.
IMHO the rationale for choosing between the two is not speed, it is 
whether you can /guarantee/ that out-of-range does not happen. If it is 
so, the library gives you a way to save a few machine code instructions.
OTOH, if you cannot guarantee this and still want the [] syntax, Bjarne 
gives explicit examples on how to implement a range-checked [] operator.

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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