io.ascii.cds does not implement some aspects of the CDS missing value specification

I found a machine-readable table on CDS that failed to read with asciitable. I compared that table with the specifications and concluded that the CDS table violated the CDS pecification for machine-readable tables. Thus, I reported this table to CDS. However, in their reply CDS states that my interpretation of the standard is not correct. Apparently, they treat the code of the fortran table reader as the authorative standard and not the documentation on the website.

Thus, this has now to be considered as an `astropy.io.ascii` bug that should be fixed.
My email exchange with the CDS is below.

Hi,

I am using
ftp://cdsarc.u-strasbg.fr/pub/cats/J/A%2BA/485/155/table4.dat
and the associated readme file:
ftp://cdsarc.u-strasbg.fr/pub/cats/J/A%2BA/485/155/ReadMe

However, my software fails to read this file. Comparing the table with the definition of machine-readable tables at http://cds.u-strasbg.fr/doc/catstd-3.4.htx#NULL
I tracked this down to an error in the ReadMe file.

In the table format description it says there

  48- 50  I3    deg    Slope      ?=- Slope in the K vs. (H-K) diagram

However, in the table NULL values are marked with "--".

Thus, this line should be:
  48- 50  I3    deg    Slope      ?=-- Slope in the K vs. (H-K) diagram

Yours,
Moritz


Dear Moritz,

The expression "?=-" means "no value when there is a string of -".
We don't have problems here with this reference.
As the standards have changed, I suggest you to re-copy the
"anafile" (I suppose that you use it) available at 
ftp://cdsarc.u-strasbg.fr/pub/sw/anafile.tar.gz

Sincerely,
          
Patricia Vannier, CDS