## Copyright (C) 2011   Lukas F. Reichlin
##
## This program 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.
##
## This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## Subscripted assignment for quaternions.
## Used by Octave for "q.key = value".

## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
## Created: November 2011
## Version: 0.2

function q = subsasgn (q, idx, val)

  switch (idx(1).type)
    case "()"                                                    # q(...) = val
      if (length (idx(1).subs) == 1 && isa (val, "quaternion"))  # required by horzcat, vertcat, cat, ...
        q(idx(1).subs{:}) = val;                                 # q = cellfun (@quaternion, varargin)
      else                                                       # general case
        val = quaternion (val);
        w = subsasgn (q.w, idx, val.w);
        x = subsasgn (q.x, idx, val.x);
        y = subsasgn (q.y, idx, val.y);
        z = subsasgn (q.z, idx, val.z);
        q = quaternion (w, x, y, z);
      endif

    case "."                                                     # q.w = val
      if (! is_real_array (val))
        error ("quaternion: subsasgn: invalid argument type, require real array");
      endif
      if (! size_equal (subsref (q.w, idx(2:end)), val))
        error ("quaternion: subsasgn: invalid argument size [%s], require dimensions [%s]", \
               num2str (size (val), "%d "), num2str (size (subsref (q.w, idx(2:end))), "%d "));
      endif
      switch (tolower (idx(1).subs))
        case {"w", "s"}
          q.w = subsasgn (q.w, idx(2:end), val);
        case {"x", "i"}
          q.x = subsasgn (q.x, idx(2:end), val);
        case {"y", "j"}
          q.y = subsasgn (q.y, idx(2:end), val);
        case {"z", "k"}
          q.z = subsasgn (q.z, idx(2:end), val);
        otherwise
          error ("quaternion: subsasgn: invalid subscript name '%s'", idx(1).subs);
      endswitch

    otherwise
      error ("quaternion: subsasgn: invalid subscript type '%s'", idx(1).type);
  endswitch

endfunction
