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Re: Question: representation of uncertainties in scientific notation

• Subject: Re: Question: representation of uncertainties in scientific notation
• From: "Herbert J. Bernstein" <yaya@xxxxxxxxxxxxxxxxxxxxxxx>
• Date: Thu, 8 Aug 2002 08:47:19 +0100 (BST)

I make use of all these forms, and they have been in CIFtbx for many
years.  I do not feel strongly that any CIF writer whould be required to
emit all of them, but I do think it would be wise to require CIF parsers
to recognize at least a significant subset of them. -- Herbert


=====================================================
 Herbert J. Bernstein, Professor of Computer Science
   Dowling College, Kramer Science Center, KSC 020
        Idle Hour Blvd, Oakdale, NY, 11769

                 +1-631-244-3035
                 yaya@dowling.edu
=====================================================

On Fri, 2 Aug 2002, Brian McMahon wrote:

> >    My understanding is the conventional crystallographic notation for a
> > number in exponential notation is
> >
> > 	-1.2345(2) x 10^1
> >
> > but my reading of section 59 in
> > http://www.iucr.org/iucr-top/cif/developers/spec/cifsyntax.html
> > is that CIF uses
> >
> > 	-1.2345e1(2)
> >
> > I just want to check that -1.2345(2)e1 is not valid and has never been
> > intended to valid in CIF.
>
> The *intention* is to specify one particular representation, namely
> -1.2345e1(2) and *not* -1.2345(2)e1. This is making concrete the usage
> implied in paragraph 5. on page 657 of Hall, Allen & Brown (1991),
> Acta Cryst. A47, 655-685.
>
> As Nick's response indicates, there are grounds for arguing in favour of
> alternative representations, but it adds a little more burden to parsers. So
> it is certainly interesting to see whether Brian T.'s question raises anyone
> who is using the other version in practice. If not, we intend to stick with
> the current single allowed format.
>
> However, I draw your attention to the fact that the current production for
> <Exponent> in the cifsyntax document generalises the Hall, Allen & Brown
> paragraph 5 to explicitly permit the following representations to be
> considered as valid:
>
>       -1.2345e1(2)
>       -1.2345E1(2)
>       -1.2345d1(2)
>       -1.2345D1(2)
>       -1.2345+1(2)
>       -1.2345e+1(2)  (etc)
>
> Again,
>    (a) is anyone currently using the 'd' or '+' forms;
>    (b) are there any strong views on this generalisation?
>
> Brian
>

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