Provide more informative error messages for various bad calling forms to set() (bug #64072) * graphics.cc (graphics_object::set (const octave_value_list& args)): Clarify summary of function. Remove unnecessary FIXME. Move BIST tests to below Fset function. * graphics.cc (Fset): Check if first argument is a string and process as NAME/VALUE pair. Provide explicit error message about what is wrong if only NAME is given and no matching VALUE. Directly call set_value_or_default() rather than forming a 2-element octave_value_list and calling set() function which accepts octave_value_list objects. Provide explicit error message if cell array of PROPERTIES is given with no following cell array of VALUES. If input validation fails just report "invalid syntax" rather than trying to suggest which input was at fault.

To cite GNU Octave in publications use:

  John W. Eaton, David Bateman, Søren Hauberg, Rik Wehbring (2023).
  GNU Octave version 8.2.0 manual: a high-level interactive language for
  numerical computations.
  URL https://www.gnu.org/software/octave/doc/v8.2.0/

A BibTeX entry for LaTeX users is:

  @manual{,
    title     = {{GNU Octave} version 8.2.0 manual: a high-level interactive language for numerical computations},
    author    = {John W. Eaton and David Bateman and S{\o}ren Hauberg and Rik Wehbring},
    year      = {2023},
    url       = {https://www.gnu.org/software/octave/doc/v8.2.0/},
  }

We have invested a lot of time and effort in creating GNU Octave, please
cite it when using it.  See also 'citation pkgname' for citing Octave
packages.