contrib/mpc/src/tanh.c

   1 /* mpc_tanh -- hyperbolic tangent of a complex number.
   2
   3 Copyright (C) 2008, 2009, 2011, 2012 INRIA
   4
   5 This file is part of GNU MPC.
   6
   7 GNU MPC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU Lesser General Public License as published by the
   9 Free Software Foundation; either version 3 of the License, or (at your
  10 option) any later version.
  11
  12 GNU MPC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  14 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
  15 more details.
  16
  17 You should have received a copy of the GNU Lesser General Public License
  18 along with this program. If not, see http://www.gnu.org/licenses/ .
  19 */
  20
  21 #include "mpc-impl.h"
  22
  23 int
  24 mpc_tanh (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd)
  25 {
  26   /* tanh(op) = -i*tan(i*op) = conj(-i*tan(conj(-i*op))) */
  27   mpc_t z;
  28   mpc_t tan_z;
  29   int inex;
  30
  31   /* z := conj(-i * op) and rop = conj(-i * tan(z)), in other words, we have
  32      to switch real and imaginary parts. Let us set them without copying
  33      significands. */
  34   mpc_realref (z)[0] = mpc_imagref (op)[0];
  35   mpc_imagref (z)[0] = mpc_realref (op)[0];
  36   mpc_realref (tan_z)[0] = mpc_imagref (rop)[0];
  37   mpc_imagref (tan_z)[0] = mpc_realref (rop)[0];
  38
  39   inex = mpc_tan (tan_z, z, MPC_RND (MPC_RND_IM (rnd), MPC_RND_RE (rnd)));
  40
  41   /* tan_z and rop parts share the same significands, copy the rest now. */
  42   mpc_realref (rop)[0] = mpc_imagref (tan_z)[0];
  43   mpc_imagref (rop)[0] = mpc_realref (tan_z)[0];
  44
  45   /* swap inexact flags for real and imaginary parts */
  46   return MPC_INEX (MPC_INEX_IM (inex), MPC_INEX_RE (inex));
  47 }