k_tanf.c revision 152741 
1/* k_tanf.c -- float version of k_tan.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5/*
6 * ====================================================
7 * Copyright 2004 Sun Microsystems, Inc.  All Rights Reserved.
8 *
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15#ifndef INLINE_KERNEL_TANF
16#ifndef lint
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/k_tanf.c 152741 2005-11-24 02:04:26Z bde $";
18#endif
19#endif
20
21#include "math.h"
22#include "math_private.h"
23
24/* |tan(x)/x - t(x)| < 2**-25.5 (~[-2e-08, 2e-08]). */
25static const double
26T[] =  {
27  0x15554d3418c99f.0p-54,	/* 0.333331395030791399758 */
28  0x1112fd38999f72.0p-55,	/* 0.133392002712976742718 */
29  0x1b54c91d865afe.0p-57,	/* 0.0533812378445670393523 */
30  0x191df3908c33ce.0p-58,	/* 0.0245283181166547278873 */
31  0x185dadfcecf44e.0p-61,	/* 0.00297435743359967304927 */
32  0x1362b9bf971bcd.0p-59,	/* 0.00946564784943673166728 */
33};
34
35#ifdef INLINE_KERNEL_TANF
36extern inline
37#endif
38float
39__kernel_tandf(double x, int iy)
40{
41	double z,r,v,w,s;
42	int32_t ix,hx;
43
44	GET_FLOAT_WORD(hx,x);
45	ix = hx&0x7fffffff;
46	z	=  x*x;
47	w 	=  z*z;
48    /* Break x^5*(T[1]+x^2*T[2]+...) into
49     *	  x^5*(T[1]+x^4*T[3]+x^8*T[5]) +
50     *	  x^5*(x^2*(T[2]+x^4*T[4]))
51     */
52	r = T[1]+w*(T[3]+w*T[5]);
53	v = z*(T[2]+w*T[4]);
54	s = z*x;
55	r = z*s*(r+v);
56	r += T[0]*s;
57	w = x+r;
58	if(iy==1) return w;
59	else return -1.0/w;
60}
61