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. */
__mpatan2(mp_no * y,mp_no * x,mp_no * z,int p)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 }
71