1/* s_tanl.c -- long double version of s_tan.c.
2 * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
3 */
4
5/* @(#)s_tan.c 5.1 93/09/24 */
6/*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17/* tanq(x)
18 * Return tangent function of x.
19 *
20 * kernel function:
21 *	__quadmath_kernel_tanq		... tangent function on [-pi/4,pi/4]
22 *	__quadmath_rem_pio2q	... argument reduction routine
23 *
24 * Method.
25 *      Let S,C and T denote the sin, cos and tan respectively on
26 *	[-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
27 *	in [-pi/4 , +pi/4], and let n = k mod 4.
28 *	We have
29 *
30 *          n        sin(x)      cos(x)        tan(x)
31 *     ----------------------------------------------------------
32 *	    0	       S	   C		 T
33 *	    1	       C	  -S		-1/T
34 *	    2	      -S	  -C		 T
35 *	    3	      -C	   S		-1/T
36 *     ----------------------------------------------------------
37 *
38 * Special cases:
39 *      Let trig be any of sin, cos, or tan.
40 *      trig(+-INF)  is NaN, with signals;
41 *      trig(NaN)    is that NaN;
42 *
43 * Accuracy:
44 *	TRIG(x) returns trig(x) nearly rounded
45 */
46
47#include "quadmath-imp.h"
48
49__float128 tanq(__float128 x)
50{
51	__float128 y[2],z=0;
52	int64_t n, ix;
53
54    /* High word of x. */
55	GET_FLT128_MSW64(ix,x);
56
57    /* |x| ~< pi/4 */
58	ix &= 0x7fffffffffffffffLL;
59	if(ix <= 0x3ffe921fb54442d1LL) return __quadmath_kernel_tanq(x,z,1);
60
61    /* tanq(Inf or NaN) is NaN */
62	else if (ix>=0x7fff000000000000LL) {
63	    if (ix == 0x7fff000000000000LL) {
64		GET_FLT128_LSW64(n,x);
65		if (n == 0)
66		    errno = EDOM;
67	    }
68	    return x-x;		/* NaN */
69	}
70
71    /* argument reduction needed */
72	else {
73	    n = __quadmath_rem_pio2q(x,y);
74	    return __quadmath_kernel_tanq(y[0],y[1],1-((n&1)<<1)); /*   1 -- n even
75							-1 -- n odd */
76	}
77}
78