contrib/mpc/src/atanh.c

   1 /* mpc_atanh -- inverse hyperbolic tangent of a complex number.
   2
   3 Copyright (C) 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_atanh (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd)
  25 {
  26   /* atanh(op) = -i*atan(i*op) */
  27   int inex;
  28   mpfr_t tmp;
  29   mpc_t z, a;
  30
  31   mpc_realref (z)[0] = mpc_imagref (op)[0];
  32   mpc_imagref (z)[0] = mpc_realref (op)[0];
  33   MPFR_CHANGE_SIGN (mpc_realref (z));
  34
  35   /* Note reversal of precisions due to later multiplication by -i */
  36   mpc_init3 (a, MPC_PREC_IM(rop), MPC_PREC_RE(rop));
  37
  38   inex = mpc_atan (a, z,
  39                    MPC_RND (INV_RND (MPC_RND_IM (rnd)), MPC_RND_RE (rnd)));
  40
  41   /* change a to -i*a, i.e., x+i*y to y-i*x */
  42   tmp[0] = mpc_realref (a)[0];
  43   mpc_realref (a)[0] = mpc_imagref (a)[0];
  44   mpc_imagref (a)[0] = tmp[0];
  45   MPFR_CHANGE_SIGN (mpc_imagref (a));
  46
  47   mpc_set (rop, a, rnd);
  48
  49   mpc_clear (a);
  50
  51   return MPC_INEX (MPC_INEX_IM (inex), -MPC_INEX_RE (inex));
  52 }