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[thirdparty/glibc.git] / sysdeps / ieee754 / dbl-64 / mpatan2.c

/*
 * IBM Accurate Mathematical Library
 * written by International Business Machines Corp.
 * Copyright (C) 2001-2020 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 <https://www.gnu.org/licenses/>.
 */
/******************************************************************/
/*  MODULE_NAME: mpatan2.c                                        */
/*                                                                */
/*  FUNCTIONS:mpatan2                                             */
/*                                                                */
/*  FILES NEEDED: mpa.h                                           */
/*                mpa.c mpatan.c mpsqrt.c                         */
/*                                                                */
/* Multi-Precision Atan2(y,x) function subroutine,                */
/* for precision p >= 4.                                          */
/* y=0 is not permitted if x<=0. No error messages are given.     */
/* The relative error of the result is bounded by 44.84*r**(1-p)  */
/* if x <= 0,  y != 0 and by 37.33*r**(1-p) if x>0. here r=2**24. */
/*                                                                */
/******************************************************************/

#include "mpa.h"

#ifndef SECTION
# define SECTION
#endif

/* Multi-Precision Atan2 (y, x) function subroutine, for p >= 4.
   y = 0 is not permitted if x <= 0. No error messages are given.  */
void
SECTION
__mpatan2 (mp_no *y, mp_no *x, mp_no *z, int p)
{
  mp_no mpt1, mpt2, mpt3;

  if (X[0] <= 0)
    {
      __dvd (x, y, &mpt1, p);
      __mul (&mpt1, &mpt1, &mpt2, p);
      if (mpt1.d[0] != 0)
	mpt1.d[0] = 1;
      __add (&mpt2, &__mpone, &mpt3, p);
      __mpsqrt (&mpt3, &mpt2, p);
      __add (&mpt1, &mpt2, &mpt3, p);
      mpt3.d[0] = Y[0];
      __mpatan (&mpt3, &mpt1, p);
      __add (&mpt1, &mpt1, z, p);
    }
  else
    {
      __dvd (y, x, &mpt1, p);
      __mpatan (&mpt1, z, p);
    }
}