## Copyright (C) 2010-2016   Lukas F. Reichlin
##
## This program 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.
##
## This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {@var{qabs} =} abs (@var{q})
## Modulus of a quaternion.
##
## @example
## q = w + x*i + y*j + z*k
## abs (q) = sqrt (w.^2 + x.^2 + y.^2 + z.^2)
## @end example
## @end deftypefn

## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
## Created: August 2010
## Version: 0.2

function b = abs (a)

  if (nargin != 1)
    print_usage ();
  endif

  b = sqrt (norm2 (a));

endfunction


%!test
%! q = quaternion (2, 3, 4, 5);
%! result = abs (q);
%! expected = sqrt (4 + 9 + 16 + 25);
%! assert (result, expected, eps);
