# Copyright (C) 1996 A. Scottedward Hodel 
#
# 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, 675 Mass Ave, Cambridge, MA 02139, USA. 
 
function x = zgshsr(y)
  # x = zgshsr(y)
  # apply householder vector based on e^(m) to 
  # (column vector) y.
  # Called by zgfslv

  # A. S. Hodel July 24, 1992
  # Conversion to Octave by R. Bruce Tenison July 3, 1994

  if(!is_vector(y))
    error(sprintf("y(%dx%d) must be a vector",rows(y),columns(y)));
  endif
  x = vec(y);
  m = length(x);
  if (m>1)
    beta = (1 + sqrt(m))*x(1) + sum(x(2:m));
    beta = beta/(m+sqrt(m));
    x(1) = x(1) - beta*(1.0d0+sqrt(m));
    x(2:m) = x(2:m) - beta*ones(m-1,1);
  else
    x = -x;
  endif
endfunction
