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e4d82761 UD |
1 | /* |
2 | * IBM Accurate Mathematical Library | |
aeb25823 | 3 | * written by International Business Machines Corp. |
2b778ceb | 4 | * Copyright (C) 2001-2021 Free Software Foundation, Inc. |
e4d82761 UD |
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 | |
cc7375ce | 8 | * the Free Software Foundation; either version 2.1 of the License, or |
e4d82761 | 9 | * (at your option) any later version. |
50944bca | 10 | * |
e4d82761 UD |
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 | |
c6c6dd48 | 14 | * GNU Lesser General Public License for more details. |
e4d82761 UD |
15 | * |
16 | * You should have received a copy of the GNU Lesser General Public License | |
5a82c748 | 17 | * along with this program; if not, see <https://www.gnu.org/licenses/>. |
e4d82761 UD |
18 | */ |
19 | /**********************************************************************/ | |
20 | /* MODULE_NAME:mptan.c */ | |
21 | /* */ | |
22 | /* FUNCTION: mptan */ | |
23 | /* */ | |
24 | /* FILES NEEDED: endian.h mpa.h */ | |
25 | /* mpa.c sincos32.c branred.c */ | |
26 | /* */ | |
27 | /* Multi-Precision tan() function subroutine, for p=32. It is based */ | |
28 | /* on the routines mpranred() and c32(). mpranred() performs range */ | |
29 | /* reduction of a double number x into a multiple precision number */ | |
30 | /* y, such that y=x-n*pi/2, abs(y)<pi/4, n=0,+-1,+-2,.... c32() */ | |
31 | /* computes both sin(y), cos(y). tan(x) is either sin(y)/cos(y) */ | |
32 | /* or -cos(y)/sin(y). The precision of the result is of about 559 */ | |
33 | /* significant bits. */ | |
34 | /* */ | |
35 | /**********************************************************************/ | |
36 | #include "endian.h" | |
37 | #include "mpa.h" | |
38 | ||
31d3cc00 UD |
39 | #ifndef SECTION |
40 | # define SECTION | |
41 | #endif | |
42 | ||
31d3cc00 UD |
43 | void |
44 | SECTION | |
b8de2202 SP |
45 | __mptan (double x, mp_no *mpy, int p) |
46 | { | |
e4d82761 UD |
47 | int n; |
48 | mp_no mpw, mpc, mps; | |
49 | ||
b8de2202 SP |
50 | /* Negative or positive result. */ |
51 | n = __mpranred (x, &mpw, p) & 0x00000001; | |
52 | /* Computing sin(x) and cos(x). */ | |
53 | __c32 (&mpw, &mpc, &mps, p); | |
54 | /* Second or fourth quarter of unit circle. */ | |
55 | if (n) | |
56 | { | |
57 | __dvd (&mpc, &mps, mpy, p); | |
c2d94018 | 58 | mpy->d[0] *= -1; |
b8de2202 SP |
59 | } |
60 | /* tan is negative in this area. */ | |
61 | else | |
62 | __dvd (&mps, &mpc, mpy, p); | |
e4d82761 | 63 | } |