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/*
* 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
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma weak __asinl = asinl
/*
* asinl(x) = atan2l(x,sqrt(1-x*x));
*
* For better accuracy, 1-x*x is computed as follows
* 1-x*x if x < 0.5,
* 2*(1-|x|)-(1-|x|)*(1-|x|) if x >= 0.5.
*
* Special cases:
* if x is NaN, return x itself;
* if |x|>1, return NaN with invalid signal.
*/
#include "libm.h"
static const long double zero = 0.0L, small = 1.0e-20L, half = 0.5L, one = 1.0L;
#ifndef lint
static const long double big = 1.0e+20L;
#endif
long double
asinl(long double x) {
long double t, w;
#ifndef lint
volatile long double dummy;
#endif
w = fabsl(x);
if (isnanl(x))
return (x + x);
else if (w <= half) {
if (w < small) {
#ifndef lint
dummy = w + big;
/* inexact if w != 0 */
#endif
return (x);
} else
return (atanl(x / sqrtl(one - x * x)));
} else if (w < one) {
t = one - w;
w = t + t;
return (atanl(x / sqrtl(w - t * t)));
} else if (w == one)
return (atan2l(x, zero)); /* asin(+-1) = +- PI/2 */
else
return (zero / zero); /* |x| > 1: invalid */
}
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