## Copyright (C) 1996 Auburn University.  All Rights Reserved
##
## 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 USA. 
 
## -*- texinfo -*-
## @deftypefn {Function File } { @var{retval} =} freqchkw ( @var{w} ) 
## Used by @code{freqresp} to check that input frequency vector @var{w} is legal.
## Returns boolean value.
## @end deftypefn

function USEW = freqchkw(w)

  ## A S Hodel July 1996

  if(isempty(w))
    USEW = 0;
  elseif(!is_vector(w))
    error(["w (",num2str(rows(w)),"x",num2str(columns(w)), ...
      "): must be [], a vector or a scalar"]);
  elseif( (max(abs(imag(w))) != 0) && (min(real(w)) <= 0) )
    error("w must have real positive entries");
  else
    w = sort(w);
    USEW = 1;   # vector provided (check values later)
  endif
endfunction