Floating point NaN values as Keywords

[Bob Garwood]

Rob Seaman wrote:
> 
> Bob Garwood <bgarwood at nrao.edu> writes:
> 
> > Pense's cfitsio library will write out "NaN" when given a keyword
> > value that is a NaN, at least under Linux and Solaris.
> 
> Is this formatted as a string in this case, or do the NaN "digits"
> appear as a real valued keyword?  The latter would be illegal.

It apears as a real valued keyword, so, I agree, this seems illegal.


Someone here just point out to me that the FITS definition allows
for the following construct as valid FITS:

K       =                      / 

i.e. no value given for the keyword.  Apparently in the FORTRAN-77
list-directed read this would be interpretted as leaving the
value of K unchanged.   For my purposes, where the desire is to
provide a required keyword for which, in some specific cases, the
value of this keyword is unknown, the above is suficient, I think
to convey that.  It doesn't provide a bogus value (i.e. it isn't
a lie) and it also doesn't omit the keyword (leaving the reader to
wonder if that was an intentional omission or not).

-Bob Garwood