sysdeps/ieee754/dbl-64/mpatan2.c

   1
   2 /*
   3  * IBM Accurate Mathematical Library
   4  * written by International Business Machines Corp.
   5  * Copyright (C) 2001 Free Software Foundation
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU Lesser General Public License as published by
   9  * the Free Software Foundation; either version 2.1 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  20  */
  21 /******************************************************************/
  22 /*  MODULE_NAME: mpatan2.c                                        */
  23 /*                                                                */
  24 /*  FUNCTIONS:mpatan2                                             */
  25 /*                                                                */
  26 /*  FILES NEEDED: mpa.h                                           */
  27 /*                mpa.c mpatan.c mpsqrt.c                         */
  28 /*                                                                */
  29 /* Multi-Precision Atan2(y,x) function subroutine,                */
  30 /* for precision p >= 4.                                          */
  31 /* y=0 is not permitted if x<=0. No error messages are given.     */
  32 /* The relative error of the result is bounded by 44.84*r**(1-p)  */
  33 /* if x <= 0,  y != 0 and by 37.33*r**(1-p) if x>0. here r=2**24. */
  34 /*                                                                */
  35 /******************************************************************/
  36
  37
  38
  39 #include "mpa.h"
  40
  41 void __mpsqrt(mp_no *, mp_no *, int);
  42 void __mpatan(mp_no *, mp_no *, int);
  43
  44 /* Multi-Precision Atan2(y,x) function subroutine, for p >= 4.    */
  45 /* y=0 is not permitted if x<=0. No error messages are given.     */
  46 void __mpatan2(mp_no *y, mp_no *x, mp_no *z, int p) {
  47
  48   static const double ZERO = 0.0, ONE = 1.0;
  49
  50   mp_no mpone = {0,{0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,
  51                     0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,
  52                     0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0}};
  53   mp_no mpt1,mpt2,mpt3;
  54
  55
  56   if (X[0] <= ZERO) {
  57     mpone.e = 1;                 mpone.d[0] = mpone.d[1] = ONE;
  58     __dvd(x,y,&mpt1,p);          __mul(&mpt1,&mpt1,&mpt2,p);
  59     if (mpt1.d[0] != ZERO)       mpt1.d[0] = ONE;
  60     __add(&mpt2,&mpone,&mpt3,p); __mpsqrt(&mpt3,&mpt2,p);
  61     __add(&mpt1,&mpt2,&mpt3,p);  mpt3.d[0]=Y[0];
  62     __mpatan(&mpt3,&mpt1,p);     __add(&mpt1,&mpt1,z,p);
  63   }
  64   else
  65   { __dvd(y,x,&mpt1,p);
  66     __mpatan(&mpt1,z,p);
  67   }
  68
  69   return;
  70 }