## Copyright (C) 2008-2019 Jaroslav Hajek
## Copyright (C) 2009 VZLU Prague
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
## <https://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn  {} {} optimget (@var{options}, @var{parname})
## @deftypefnx {} {} optimget (@var{options}, @var{parname}, @var{default})
## Return the specific option @var{parname} from the optimization options
## structure @var{options} created by @code{optimset}.
##
## If @var{parname} is not defined then return @var{default} if supplied,
## otherwise return an empty matrix.
## @seealso{optimset}
## @end deftypefn

function retval = optimget (options, parname, default)

  if (nargin < 2 || nargin > 4 || ! isstruct (options) || ! ischar (parname))
    print_usage ();
  endif

  ## Expand partial-length names into full names
  opts = __all_opts__ ();
  idx = strncmpi (opts, parname, length (parname));
  nmatch = sum (idx);

  if (nmatch == 1)
    parname = opts{idx};
  elseif (nmatch == 0)
    warning ("optimget: unrecognized option: %s", parname);
  else
    fmt = sprintf ("optimget: ambiguous option: %%s (%s%%s)",
                   repmat ("%s, ", 1, nmatch-1));
    warning (fmt, parname, opts{idx});
  endif

  if (isfield (options, parname) && ! isempty (options.(parname)))
    retval = options.(parname);
  elseif (nargin > 2)
    retval = default;
  else
    retval = [];
  endif

endfunction


%!shared opts
%! opts = optimset ("tolx", 0.1, "maxit", 100);
%!assert (optimget (opts, "TolX"), 0.1)
%!assert (optimget (opts, "maxit"), 100)
%!assert (optimget (opts, "MaxITer"), 100)
%!assert (optimget (opts, "TolFun"), [])
%!assert (optimget (opts, "TolFun", 1e-3), 1e-3)

## Test input validation
%!error optimget ()
%!error optimget (1)
%!error optimget (1,2,3,4,5)
%!error optimget (1, "name")
%!error optimget (struct (), 2)
%!warning <unrecognized option: foobar> (optimget (opts, "foobar"));
%!warning <ambiguous option: Max> (optimget (opts, "Max"));
