/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
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*/
/*
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
* tanl(x)
* Table look-up algorithm by K.C. Ng, November, 1989.
*
* kernel function:
* __k_tanl ... tangent function on [-pi/4,pi/4]
* __rem_pio2l ... argument reduction routine
*
* Method.
* Let S and C denote the sin and cos respectively on [-PI/4, +PI/4].
* 1. Assume the argument x is reduced to y1+y2 = x-k*pi/2 in
* [-pi/2 , +pi/2], and let n = k mod 4.
* 2. Let S=S(y1+y2), C=C(y1+y2). Depending on n, we have
*
* n sin(x) cos(x) tan(x)
* ----------------------------------------------------------
* 0 S C S/C
* 1 C -S -C/S
* 2 -S -C S/C
* 3 -C S -C/S
* ----------------------------------------------------------
*
* Special cases:
* Let trig be any of sin, cos, or tan.
* trig(+-INF) is NaN, with signals;
* trig(NaN) is that NaN;
*
* Accuracy:
* computer TRIG(x) returns trig(x) nearly rounded.
*/
#pragma weak __tanl = tanl
#include "libm.h"
#include "longdouble.h"
long double
tanl(long double x) {
long double y[2], z = 0.0L;
int n, ix;
ix = *(int *) &x; /* High word of x */
ix &= 0x7fffffff;
if (ix <= 0x3ffe9220) /* |x| ~< pi/4 */
return (__k_tanl(x, z, 0));
else if (ix >= 0x7fff0000) /* trig(Inf or NaN) is NaN */
return (x - x);
else { /* argument reduction needed */
n = __rem_pio2l(x, y);
return (__k_tanl(y[0], y[1], (n & 1)));
}
}