## Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2002, 2004,
##               2005, 2006, 2007 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 3 of the License, 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, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} polyval (@var{c}, @var{x})
## Evaluate a polynomial.
##
## @code{polyval (@var{c}, @var{x})} will evaluate the polynomial at the
## specified value of @var{x}.
##
## If @var{x} is a vector or matrix, the polynomial is evaluated at each of
## the elements of @var{x}.
## @seealso{polyvalm, poly, roots, conv, deconv, residue, filter,
## polyderiv, polyinteg}
## @end deftypefn

## Author: Tony Richardson <arichard@stark.cc.oh.us>
## Created: June 1994
## Adapted-By: jwe

function y = polyval (c, x)

  if (nargin != 2)
    print_usage ();
  endif

  if (! (isvector (c) || isempty (c)))
    error ("polyval: first argument must be a vector");
  endif

  if (isempty (x))
    y = [];
    return;
  endif

  if (length (c) == 0)
    y = c;
    return;
  endif

  n = length (c);
  y = c (1) * ones (rows (x), columns (x));
  for index = 2:n
    y = c (index) + x .* y;
  endfor

endfunction

%!assert(polyval ([1, 1, 1], 2) == 7);

%!assert(all (all (polyval ([1, 1, 1], [0; 1; 2]) == [1; 3; 7])));

%!assert(isempty (polyval ([1, 1, 1], [])));

%!assert(all (all (polyval ([1, 1, 1], [-1, 0; 1, 2]) == [1, 1; 3, 7])));

%!error polyval ([1, 2; 3, 4], [-1, 0; 1, 2]);

%!assert(isempty (polyval ([], [-1, 0; 1, 2])));