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Re: Specification error for Math.round

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On Thu, 11 Oct 2012 21:46:33 -0700, RobG wrote:

> On Friday, 12 October 2012 06:16:03 UTC+10, Danny  wrote:

>> Math wise, usually x+0.5 should give x+1 as a rounded figure
> 
> Not at all. If x is a decimal, then:
> 
>     2.75 rounds to 3 2.75 + 0.5 = 3.25 which also rounds to 3
> 
> If x is an integer, then for simple rounding you are correct.

I suspect that was the case that Danny was referring to.

Normally, for any "whole number" x.0, I would expect decimal fractions in 
the range (x.0 - 0.5) .. (x.0 + 0.49999999999999999999999999..) to round 
to x.

I think this is what you get if your rounding function f(x) is 
{return Math.floor(x+0.5);}

I think (1) it's probably better to keep your numbers away from the cases 
where errors may occur, and (2) if you want to process numbers with that 
much precision, don't use javascript.

Rgds

Denis McMahon

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Specification error for Math.round RobG <rgqld@iinet.net.au> - 2012-10-10 19:52 -0700
  Re: Specification error for Math.round Patricia Shanahan <pats@acm.org> - 2012-10-11 07:29 +0100
    Re: Specification error for Math.round Dr J R Stockton <reply1241@merlyn.demon.co.uk.invalid> - 2012-10-12 23:00 +0100
  Re: Specification error for Math.round Danny <dann90038@gmail.com> - 2012-10-11 13:16 -0700
    Re: Specification error for Math.round Patricia Shanahan <pats@acm.org> - 2012-10-12 00:14 +0100
    Re: Specification error for Math.round RobG <rgqld@iinet.net.au> - 2012-10-11 21:46 -0700
      Re: Specification error for Math.round Patricia Shanahan <pats@acm.org> - 2012-10-12 08:28 +0100
        Re: Specification error for Math.round Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-10-13 22:14 +0200
          Re: Specification error for Math.round Patricia Shanahan <pats@acm.org> - 2012-10-13 21:45 +0100
            Re: Specification error for Math.round "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2012-10-13 23:59 +0200
        Re: Specification error for Math.round Dr J R Stockton <reply1241@merlyn.demon.co.uk.invalid> - 2012-10-13 19:31 +0100
      Re: Specification error for Math.round Denis McMahon <denismfmcmahon@gmail.com> - 2012-10-14 11:09 +0000
  Re: Specification error for Math.round Dr J R Stockton <reply1241@merlyn.demon.co.uk.invalid> - 2012-10-12 22:48 +0100

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