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/* s_tanl.c -- long double version of s_tan.c.
* Conversion to long double by Ulrich Drepper,
* Cygnus Support, drepper@cygnus.com.
*/
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: $";
#endif
/* tanl(x)
* Return tangent function of x.
*
* kernel function:
* __kernel_tanl ... tangent function on [-pi/4,pi/4]
* __ieee754_rem_pio2l ... argument reduction routine
*
* Method.
* Let S,C and T denote the sin, cos and tan respectively on
* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
* in [-pi/4 , +pi/4], and let n = k mod 4.
* We have
*
* n sin(x) cos(x) tan(x)
* ----------------------------------------------------------
* 0 S C T
* 1 C -S -1/T
* 2 -S -C T
* 3 -C S -1/T
* ----------------------------------------------------------
*
* Special cases:
* Let trig be any of sin, cos, or tan.
* trig(+-INF) is NaN, with signals;
* trig(NaN) is that NaN;
*
* Accuracy:
* TRIG(x) returns trig(x) nearly rounded
*/
#include <errno.h>
#include <math.h>
#include <math_private.h>
#include <libm-alias-ldouble.h>
long double __tanl(long double x)
{
long double y[2],z=0.0;
int32_t n, se, i0, i1;
/* High word of x. */
GET_LDOUBLE_WORDS(se,i0,i1,x);
/* |x| ~< pi/4 */
se &= 0x7fff;
if(se <= 0x3ffe) return __kernel_tanl(x,z,1);
/* tan(Inf or NaN) is NaN */
else if (se==0x7fff) {
if (i1 == 0 && i0 == 0x80000000)
__set_errno (EDOM);
return x-x;
}
/* argument reduction needed */
else {
n = __ieee754_rem_pio2l(x,y);
return __kernel_tanl(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even
-1 -- n odd */
}
}
libm_alias_ldouble (__tan, tan)
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