[Israel.pm] Number imprecision

Peter Gordon peter at pg-consultants.com
Tue Sep 5 02:38:46 PDT 2006


There is a concern that 1-$x might go negative, so how about
sqrt(abs(1-$x)) 

Regards,

Peter

On Mon, 2006-09-04 at 11:25 +0200, Michael Gang wrote:
> Dear Mr Gordon,
> 
> What I am making in this case sqrt(1- $x) ?
> Should I add a small number like this sqrt(1.000000001-$x) or is there
> a more elegant answer ?
> 
> Best regards,
> Michael
> On 9/4/06, perl-request at perl.org.il <perl-request at perl.org.il>am ma wrote:
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> >    1. Re: Fwd: number imprecision (Peter Gordon)
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> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Sun, 03 Sep 2006 14:01:51 +0300
> > From: Peter Gordon <peter at pg-consultants.com>
> > Subject: Re: [Israel.pm] Fwd: number imprecision
> > To: Perl in Israel <perl at perl.org.il>
> > Message-ID: <1157281311.2705.15.camel at tigger>
> > Content-Type: text/plain
> >
> > Since $x is the result of a floating point calculation,
> > do the following test instead
> >
> > abs(1-$x) < 0.00000001
> >
> > Peter
> >
> > On Sun, 2006-09-03 at 09:50 +0200, Michael Gang wrote:
> > > Dear All,
> > >
> > > I have encountered a strange calculation in perl.
> > > I have a value which i get in the function ($x ) and his value is 1 .
> > > Now i show from the debugger a snippet.
> > >
> > > DB<3> x $x
> > > 0  1
> > > DB<4> x 1-$x
> > >  '-2.22044604925031e-16'
> > >
> > >
> > >
> > > Has anyone an explanation of it how 1-1=  '-2.22044604925031e-16' ?
> > >
> > > Thanks in advance,
> > > Michael
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