### Copyright (C) 1996 John W. Eaton
###
### 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 2, 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, write to the Free
### Software Foundation, 59 Temple Place - Suite 330, Boston, MA
### 02111-1307, USA.

## usage: complement (a, b)
##
## Returns the elements of set b that are not in set a.
##
## See - create_set, union, intersection

function y = complement (a, b)

  if (nargin != 2)
    usage ("complement(a,b)");
  endif

  if (isempty (a))
    y = create_set(b);
  elseif (isempty (b))
    y = [];
  else
    a = create_set (a);
    b = create_set (b);
    yindex = 1;
    y = zeros (1, length (b));
    for index = 1:length (b)
      if (all (a != b (index)))
        y(yindex++) = b(index);
      endif
    endfor
    y = y(1:(yindex-1));
  endif

endfunction