| /* |
| * IBM Accurate Mathematical Library |
| * written by International Business Machines Corp. |
| * Copyright (C) 2001-2014 Free Software Foundation, Inc. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU Lesser General Public License as published by |
| * the Free Software Foundation; either version 2.1 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public License |
| * along with this program; if not, see <http://www.gnu.org/licenses/>. |
| */ |
| /**********************************************************************/ |
| /* MODULE_NAME:mptan.c */ |
| /* */ |
| /* FUNCTION: mptan */ |
| /* */ |
| /* FILES NEEDED: endian.h mpa.h */ |
| /* mpa.c sincos32.c branred.c */ |
| /* */ |
| /* Multi-Precision tan() function subroutine, for p=32. It is based */ |
| /* on the routines mpranred() and c32(). mpranred() performs range */ |
| /* reduction of a double number x into a multiple precision number */ |
| /* y, such that y=x-n*pi/2, abs(y)<pi/4, n=0,+-1,+-2,.... c32() */ |
| /* computes both sin(y), cos(y). tan(x) is either sin(y)/cos(y) */ |
| /* or -cos(y)/sin(y). The precision of the result is of about 559 */ |
| /* significant bits. */ |
| /* */ |
| /**********************************************************************/ |
| #include "endian.h" |
| #include "mpa.h" |
| |
| #ifndef SECTION |
| # define SECTION |
| #endif |
| |
| void |
| SECTION |
| __mptan (double x, mp_no *mpy, int p) |
| { |
| int n; |
| mp_no mpw, mpc, mps; |
| |
| /* Negative or positive result. */ |
| n = __mpranred (x, &mpw, p) & 0x00000001; |
| /* Computing sin(x) and cos(x). */ |
| __c32 (&mpw, &mpc, &mps, p); |
| /* Second or fourth quarter of unit circle. */ |
| if (n) |
| { |
| __dvd (&mpc, &mps, mpy, p); |
| mpy->d[0] *= -1; |
| } |
| /* tan is negative in this area. */ |
| else |
| __dvd (&mps, &mpc, mpy, p); |
| } |