| |
| /* |
| * IBM Accurate Mathematical Library |
| * written by International Business Machines Corp. |
| * Copyright (C) 2001 Free Software Foundation |
| * |
| * 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, write to the Free Software |
| * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| */ |
| /**********************************************************************/ |
| /* 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" |
| |
| int __mpranred(double, mp_no *, int); |
| void __c32(mp_no *, mp_no *, mp_no *, int); |
| |
| void __mptan(double x, mp_no *mpy, int p) { |
| |
| static const double MONE = -1.0; |
| |
| int n; |
| mp_no mpw, mpc, mps; |
| |
| n = __mpranred(x, &mpw, p) & 0x00000001; /* negative or positive result */ |
| __c32(&mpw, &mpc, &mps, p); /* computing sin(x) and cos(x) */ |
| if (n) /* second or fourth quarter of unit circle */ |
| { __dvd(&mpc,&mps,mpy,p); |
| mpy->d[0] *= MONE; |
| } /* tan is negative in this area */ |
| else __dvd(&mps,&mpc,mpy,p); |
| |
| return; |
| } |