## Copyright (C) 1994, 1996, 1997, 2000, 2004, 2005, 2006, 2007, 2008
##               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 {Mapping Function} {} acoth (@var{x})
## Compute the inverse hyperbolic cotangent of each element of @var{x}.
## @end deftypefn

## Author: jwe

function w = acoth (z)

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

  w = atanh (1 ./ z);

endfunction

%!test
%! rt2 = sqrt (2);
%! rt3 = sqrt (3);
%! v = -i*[pi/6, pi/4, pi/3, -pi/3, -pi/4, -pi/6];
%! x = i*[rt3, 1, rt3/3, -rt3/3, -1, -rt3];
%! assert(all (abs (acoth (x) - v) < sqrt (eps)));

%!error acoth ();

%!error acoth (1, 2);