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##
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## distribution or <https://octave.org/copyright/>.
##
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## -*- texinfo -*-
## @deftypefn  {} {@var{val} =} odeget (@var{ode_opt}, @var{field})
## @deftypefnx {} {@var{val} =} odeget (@var{ode_opt}, @var{field}, @var{default})
##
## Query the value of the property @var{field} in the ODE options structure
## @var{ode_opt}.
##
## If called with two input arguments and the first input argument
## @var{ode_opt} is an ODE option structure and the second input argument
## @var{field} is a string specifying an option name, then return the option
## value @var{val} corresponding to @var{field} from @var{ode_opt}.
##
## If called with an optional third input argument, and @var{field} is
## not set in the structure @var{ode_opt}, then return the default value
## @var{default} instead.
## @seealso{odeset}
## @end deftypefn

function val = odeget (ode_opt, field, default = [])

  if (nargin < 2)
    print_usage ();
  endif

  validateattributes (ode_opt, {"struct"}, {"nonempty"});
  validateattributes (field, {"char"}, {"nonempty"});

  if (! isfield (ode_opt, field))
    error ("Octave:odeget:InvalidPropName",
           'odeget: Unrecognized property name "%s".', field);
  else
    val = ode_opt.(field);
    if (isempty (val))
      val = default;
    endif
  endif

endfunction


%!demo
%! ## Return the manually changed value RelTol of the ODE options
%! ## structure A.  If RelTol wouldn't have been changed then an
%! ## empty matrix value would have been returned.
%!
%! A = odeset ("RelTol", 1e-1, "AbsTol", 1e-2);
%! odeget (A, "RelTol", [])

%!assert (odeget (odeset (), "RelTol"), [])
%!assert (odeget (odeset ("RelTol", 10), "RelTol"), 10)
%!assert (odeget (odeset (), "RelTol", 10), 10)
%!assert (odeget (odeset (), "Stats"), [])
%!assert (odeget (odeset (), "Stats", "on"), "on")
%!assert (odeget (odeset (), "Mass"), [])
%!assert (odeget (odeset (), "AbsTol", 1e-9), 1e-9)
%!assert (odeget (odeset ("AbsTol", 1e-9), "AbsTol", []), 1e-9)
%!test
%! warning ("off", "Octave:invalid-input-arg", "local");
%! assert (odeget (odeset ("foo", 42), "foo"), 42);

## Test input validation
%!error <Invalid call> odeget ()
%!error <Invalid call> odeget (1)
%!error odeget (1, "opt1")
%!error odeget (struct ("opt1", 1), 1)
%!error odeget (struct ("opt1", 1), "foo")
