ADQL: MOD sign

[Mark Taylor]

Dave & Marco,

the cosmopterix page you reference states "PostgreSQL requires both
parameters to be integers."  I don't have a tame PostgreSQL
instance locally to play with, but looking at the online docs
and other circumstantial evidence suggests that it does work
in PostgreSQL (semantics remainder of y/x) with floating point
arguments too.  Is this integer restriction actually true for
PostgreSQL and/or other backends?  Although one thinks of MOD
as an integer thing, the floating point form may be useful in
some cases, so it's probably not a good idea to make this
restriction unless there's a good reason for it.

Mark

On Thu, 11 Aug 2016, Marco Molinaro wrote:

> Hi Dave,
> if nobody complains I suggest to use that text and explicit the
> parameters to be integers to preserve back end homogeneity.
> 
> Cheers,
>      Marco
> 
> 2016-07-19 14:49 GMT+02:00 Dave Morris <dave.morris at metagrid.co.uk>:
> > Hi Marco,
> >
> > On 2016-07-12 14:16, Marco Molinaro wrote:
> >>
> >>
> >> I still like to know whether we should put something about the
> >> sign preservation in the modulo in the ADQL-2.1 WD
> >>
> >
> > Yes, I think we should define this in the 2.1 specification.
> >
> > Based on the results from Cosmopterix, we should limit the parameters to
> > integer values.
> > https://github.com/ivoa/cosmopterix/wiki/MOD-for-negative-numbers
> >
> > I like the text you put in the errata, so is this appropriate for the
> > standard ?
> >
> > --------
> >
> >     The modulo operator returns the remainder, R, of the division of two
> > integer values, M / N
> >
> >         M % N = R
> >
> >     where
> >
> >         R has the same sign as M
> >         |R| is less than |N|
> >         M = (K * N) + R for a given integer K
> >
> > --------
> >
> >
> > Cheers,
> > Dave
> >
> >
> > --------
> > Dave Morris
> > Software Developer
> > Wide Field Astronomy Unit
> > Institute for Astronomy
> > University of Edinburgh
> > --------
> >
> 

--
Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-9288776  http://www.star.bris.ac.uk/~mbt/