ADQL XMATCH

[Arnold Rots]

Maybe not surprisingly, I favor Walter's proposal.
It has the distinct advantage that it is extensible
and does not paint us into a corner.
For instance, at some point the need may arise
for distances in Cartesian coordinates
(3-D spatial distances).

  - Arnold

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Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
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On Thu, Apr 7, 2016 at 4:43 AM, Markus Demleitner <
msdemlei at ari.uni-heidelberg.de> wrote:

> Hi Walter,
>
> On Wed, Apr 06, 2016 at 11:14:17AM -0700, Walter Landry wrote:
> > Marco Molinaro <molinaro at oats.inaf.it> wrote:
> >
> > Since no one commented on it before, I would like to repeat my
> > proposal for a point literal.
> >
> >   {a,b} -> POINT('ICRS GEOCENTER',a,b)
> >
> > Then the distance function would be
> >
> >   DISTANCE({ra1,dec1},{ra2,dec2})
> >
> > This would keep the function type safe and obviate the need for a new
> > overload for DISTANCE.
>
> I suppose everyone was more or less like me: Nice, but is it really
> worth introducing new syntax?  And will this be trouble later, when
> we (perhaps) may deal with array literals?  Not sure.  Ah, let
> someone else worry about it.
>
> So, I can't give you more than a heartfelt "undecided".
>
>
> DISTANCE with four floating-point arguments, on the other hand, sits
> nicely in my comfort zone of probably making the average astronomer
> happy while being very cheap -- after all, we have other functions
> that admit a variable number of arguments and change behaviour
> depending on the arity used. I'll just mention random here.
>
> Cheers,
>
>          Markus
>
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