/*

 * IBM Accurate Mathematical Library

 * written by International Business Machines Corp.

 * Copyright (C) 2001-2018 Free Software Foundation, Inc.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program; if not, see <http://www.gnu.org/licenses/>.

 */

/**********************************************************************/

/* MODULE_NAME:mptan.c                                                */

/*                                                                    */

/* FUNCTION: mptan                                                    */

/*                                                                    */

/* FILES NEEDED: endian.h  mpa.h                                      */

/*               mpa.c  sincos32.c branred.c                          */

/*                                                                    */

/* Multi-Precision tan() function subroutine, for p=32.  It is based  */

/* on the routines mpranred() and c32(). mpranred() performs range    */

/* reduction of a double number x into a multiple precision number    */

/* y, such that y=x-n*pi/2, abs(y)

/* computes both sin(y), cos(y).  tan(x) is either sin(y)/cos(y)      */

/* or -cos(y)/sin(y). The precision of the result is of about 559     */

/* significant bits.                                                  */

/*                                                                    */

/**********************************************************************/

#include "endian.h"

#include "mpa.h"

#ifndef SECTION

# define SECTION

#endif

void

SECTION

__mptan (double x, mp_no *mpy, int p)

{

  int n;

  mp_no mpw, mpc, mps;

  /* Negative or positive result.  */

  n = __mpranred (x, &mpw, p) & 0x00000001;

  /* Computing sin(x) and cos(x).  */

  __c32 (&mpw, &mpc, &mps, p);

  /* Second or fourth quarter of unit circle.  */

  if (n)

    {

      __dvd (&mpc, &mps, mpy, p);

      mpy->d[0] *= -1;

    }

  /* tan is negative in this area.  */

  else

    __dvd (&mps, &mpc, mpy, p);

}