sysdeps/ieee754/dbl-64/mpatan2.c

   1 /*
   2  * IBM Accurate Mathematical Library
   3  * written by International Business Machines Corp.
   4  * Copyright (C) 2001-2016 Free Software Foundation, Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19 /******************************************************************/
  20 /*  MODULE_NAME: mpatan2.c                                        */
  21 /*                                                                */
  22 /*  FUNCTIONS:mpatan2                                             */
  23 /*                                                                */
  24 /*  FILES NEEDED: mpa.h                                           */
  25 /*                mpa.c mpatan.c mpsqrt.c                         */
  26 /*                                                                */
  27 /* Multi-Precision Atan2(y,x) function subroutine,                */
  28 /* for precision p >= 4.                                          */
  29 /* y=0 is not permitted if x<=0. No error messages are given.     */
  30 /* The relative error of the result is bounded by 44.84*r**(1-p)  */
  31 /* if x <= 0,  y != 0 and by 37.33*r**(1-p) if x>0. here r=2**24. */
  32 /*                                                                */
  33 /******************************************************************/
  34
  35 #include "mpa.h"
  36
  37 #ifndef SECTION
  38 # define SECTION
  39 #endif
  40
  41 /* Multi-Precision Atan2 (y, x) function subroutine, for p >= 4.
  42    y = 0 is not permitted if x <= 0. No error messages are given.  */
  43 void
  44 SECTION
  45 __mpatan2 (mp_no *y, mp_no *x, mp_no *z, int p)
  46 {
  47   mp_no mpt1, mpt2, mpt3;
  48
  49   if (X[0] <= 0)
  50     {
  51       __dvd (x, y, &mpt1, p);
  52       __mul (&mpt1, &mpt1, &mpt2, p);
  53       if (mpt1.d[0] != 0)
  54         mpt1.d[0] = 1;
  55       __add (&mpt2, &__mpone, &mpt3, p);
  56       __mpsqrt (&mpt3, &mpt2, p);
  57       __add (&mpt1, &mpt2, &mpt3, p);
  58       mpt3.d[0] = Y[0];
  59       __mpatan (&mpt3, &mpt1, p);
  60       __add (&mpt1, &mpt1, z, p);
  61     }
  62   else
  63     {
  64       __dvd (y, x, &mpt1, p);
  65       __mpatan (&mpt1, z, p);
  66     }
  67 }