Re: [Plplot-general] Font setting parameters in Fortran90.

[Alan W. I. <ir...@be...>]

On 2013-10-29 21:59-0000 James Tappin wrote:

> It appears that in the Fortran 95 binding in 5.9.10, the font setting
> constants (PL_FCI_SANS etc.) have become variables. In
> bindings/f95/plplot_parameters.h we now have
>
>      integer :: PL_FCI_SANS
>      data PL_FCI_SANS / z'0' /
> in place of
>
>      integer, parameter :: PL_FCI_SANS = z'0'
>
> Which cannot be used in a data initialization such as:
>
>  integer, parameter, dimension(*) :: font_list = [PL_FCI_SANS,
> PL_FCI_SERIF, &
>       & PL_FCI_MONO, PL_FCI_SCRIPT, PL_FCI_SYMBOL]
>
> Is there a good reason for this or is it a regression?

bindings/f95/plplot_parameters.h is generated automatically by a sed
script that has been deliberately designed to create two styles in the
results.  One of those styles is the data style that you don't like,
and the other the parameter style you prefer.  The script uses the
data style for all hexadecimal (e.g., z'0') constants and the
parameter style for all normal integers.  What happened in
the above change was that we changed to hexadecimal constants for
all bit fields in our API.  All such data are powers of two so
the hexadecimal form is a lot easier to understand.

Of course, the important question s why we support two styles in that
sed script?  I am sure we did that deliberately with the motivation of
wanting to support a wide range of Fortran compilers.  In other
words we were worried that some
of them might complain about

integer, parameter :: PL_FCI_SANS = z'0'

but the data form that we use now should work for all of them.

The gfortran info documentation says something about this.

<quote>
Up to Fortran 95, BOZ literals [i.e., constants started with b', o',
or z'] were only allowed to initialize integer
variables in DATA statements.  Since Fortran 2003 BOZ literals are
also allowed as argument of REAL', DBLE', INT' and CMPLX'; the result
is the same as if the integer BOZ literal had been converted by
TRANSFER' to, respectively, real', double precision', integer' or
complex'.  As GNU Fortran extension the intrinsic procedures FLOAT',
DFLOAT', COMPLEX' and DCMPLX' are treated alike. 
</quote>

They then go on to say they support BOZ constants generally as an
extension to the Fortran standards prior to Fortran 2003.  So I assume
the above statement would work with gfortran, but because of the
uncertainty about whether it would work with other fortran compilers
we went with the conservative approach of sticking with the data style
for BOZ constants.

@Arjen: are we being too cautious here?  I note from
http://gcc.gnu.org/wiki/Fortran2003 that gfortran already has almost
complete support for Fortran 2003 (and certainly the general BOZ
support), and I wonder if other fortran compilers are typically also
compliant with Fortran 2003, at least to the extent of general support
for integer parameter style above for BOZ constants?

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
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