1 /* k_tanf.c -- float version of k_tan.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
4 * $FreeBSD: src/lib/msun/src/k_tanf.c,v 1.5 1999/08/28 00:06:42 peter Exp $
5 * $DragonFly: src/lib/msun/src/Attic/k_tanf.c,v 1.2 2003/06/17 04:26:53 dillon Exp $
9 * ====================================================
10 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
12 * Developed at SunPro, a Sun Microsystems, Inc. business.
13 * Permission to use, copy, modify, and distribute this
14 * software is freely granted, provided that this notice
16 * ====================================================
20 #include "math_private.h"
26 one = 1.0000000000e+00, /* 0x3f800000 */
27 pio4 = 7.8539812565e-01, /* 0x3f490fda */
28 pio4lo= 3.7748947079e-08, /* 0x33222168 */
30 3.3333334327e-01, /* 0x3eaaaaab */
31 1.3333334029e-01, /* 0x3e088889 */
32 5.3968254477e-02, /* 0x3d5d0dd1 */
33 2.1869488060e-02, /* 0x3cb327a4 */
34 8.8632395491e-03, /* 0x3c11371f */
35 3.5920790397e-03, /* 0x3b6b6916 */
36 1.4562094584e-03, /* 0x3abede48 */
37 5.8804126456e-04, /* 0x3a1a26c8 */
38 2.4646313977e-04, /* 0x398137b9 */
39 7.8179444245e-05, /* 0x38a3f445 */
40 7.1407252108e-05, /* 0x3895c07a */
41 -1.8558637748e-05, /* 0xb79bae5f */
42 2.5907305826e-05, /* 0x37d95384 */
46 float __kernel_tanf(float x, float y, int iy)
48 float __kernel_tanf(x, y, iy)
55 ix = hx&0x7fffffff; /* high word of |x| */
56 if(ix<0x31800000) /* x < 2**-28 */
57 {if((int)x==0) { /* generate inexact */
58 if((ix|(iy+1))==0) return one/fabsf(x);
59 else return (iy==1)? x: -one/x;
62 if(ix>=0x3f2ca140) { /* |x|>=0.6744 */
63 if(hx<0) {x = -x; y = -y;}
70 /* Break x^5*(T[1]+x^2*T[2]+...) into
71 * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
72 * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
74 r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
75 v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
77 r = y + z*(s*(r+v)+y);
82 return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
85 else { /* if allow error up to 2 ulp,
86 simply return -1.0/(x+r) here */
87 /* compute -1.0/(x+r) accurately */
92 SET_FLOAT_WORD(z,i&0xfffff000);
93 v = r-(z - x); /* z+v = r+x */
94 t = a = -(float)1.0/w; /* a = -1.0/w */
96 SET_FLOAT_WORD(t,i&0xfffff000);