function y = complement(a,b)

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

  if(nargin != 2)
    error("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