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glibc  2.9
mpatan2.c
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00001 
00002 /*
00003  * IBM Accurate Mathematical Library
00004  * written by International Business Machines Corp.
00005  * Copyright (C) 2001 Free Software Foundation
00006  *
00007  * This program is free software; you can redistribute it and/or modify
00008  * it under the terms of the GNU Lesser General Public License as published by
00009  * the Free Software Foundation; either version 2.1 of the License, or
00010  * (at your option) any later version.
00011  *
00012  * This program is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public License
00018  * along with this program; if not, write to the Free Software
00019  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
00020  */
00021 /******************************************************************/
00022 /*  MODULE_NAME: mpatan2.c                                        */
00023 /*                                                                */
00024 /*  FUNCTIONS:mpatan2                                             */
00025 /*                                                                */
00026 /*  FILES NEEDED: mpa.h                                           */
00027 /*                mpa.c mpatan.c mpsqrt.c                         */
00028 /*                                                                */
00029 /* Multi-Precision Atan2(y,x) function subroutine,                */
00030 /* for precision p >= 4.                                          */
00031 /* y=0 is not permitted if x<=0. No error messages are given.     */
00032 /* The relative error of the result is bounded by 44.84*r**(1-p)  */
00033 /* if x <= 0,  y != 0 and by 37.33*r**(1-p) if x>0. here r=2**24. */
00034 /*                                                                */
00035 /******************************************************************/
00036 
00037 
00038 
00039 #include "mpa.h"
00040 
00041 void __mpsqrt(mp_no *, mp_no *, int);
00042 void __mpatan(mp_no *, mp_no *, int);
00043 
00044 /* Multi-Precision Atan2(y,x) function subroutine, for p >= 4.    */
00045 /* y=0 is not permitted if x<=0. No error messages are given.     */
00046 void __mpatan2(mp_no *y, mp_no *x, mp_no *z, int p) {
00047 
00048   static const double ZERO = 0.0, ONE = 1.0;
00049 
00050   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,
00051                     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,
00052                     0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0}};
00053   mp_no mpt1,mpt2,mpt3;
00054 
00055 
00056   if (X[0] <= ZERO) {
00057     mpone.e = 1;                 mpone.d[0] = mpone.d[1] = ONE;
00058     __dvd(x,y,&mpt1,p);          __mul(&mpt1,&mpt1,&mpt2,p);
00059     if (mpt1.d[0] != ZERO)       mpt1.d[0] = ONE;
00060     __add(&mpt2,&mpone,&mpt3,p); __mpsqrt(&mpt3,&mpt2,p);
00061     __add(&mpt1,&mpt2,&mpt3,p);  mpt3.d[0]=Y[0];
00062     __mpatan(&mpt3,&mpt1,p);     __add(&mpt1,&mpt1,z,p);
00063   }
00064   else
00065   { __dvd(y,x,&mpt1,p);
00066     __mpatan(&mpt1,z,p);
00067   }
00068 
00069   return;
00070 }