w_acosh.c

标准c库代码,可以应用于各个系统提供了大量的基本函数

/* @(#)w_acosh.c 5.1 93/09/24 */
/*
 * ====================================================
 * 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.
 * ====================================================
 *
 */

/*
FUNCTION
<<acosh>>, <<acoshf>>---inverse hyperbolic cosine 

INDEX
acosh
INDEX
acoshf

ANSI_SYNOPSIS
	#include <math.h>
	double acosh(double <[x]>);
	float acoshf(float <[x]>);

TRAD_SYNOPSIS
	#include <math.h>
	double acosh(<[x]>)
	double <[x]>;

	float acoshf(<[x]>)
	float <[x]>;

DESCRIPTION
<<acosh>> calculates the inverse hyperbolic cosine of <[x]>.
<<acosh>> is defined as 
@ifinfo
. log(<[x]> + sqrt(<[x]>*<[x]>-1))
@end ifinfo
@tex
$$ln\Bigl(x + \sqrt{x^2-1}\Bigr)$$
@end tex

<[x]> must be a number greater than or equal to 1.

<<acoshf>> is identical, other than taking and returning floats.

RETURNS
<<acosh>> and <<acoshf>> return the calculated value.  If <[x]> 
less than 1, the return value is NaN and <<errno>> is set to <<EDOM>>.

You can change the error-handling behavior with the non-ANSI
<<matherr>> function.

PORTABILITY
Neither <<acosh>> nor <<acoshf>> are ANSI C.  They are not recommended
for portable programs.


QUICKREF ANSI SVID POSIX RENTRANT
 acos	 n,n,n,m
 acosf   n,n,n,m

MATHREF  
 acosh, NAN,   arg,DOMAIN,EDOM
 acosh, < 1.0, NAN,DOMAIN,EDOM
 acosh, >=1.0, acosh(arg),,,

MATHREF
 acoshf, NAN,   arg,DOMAIN,EDOM
 acoshf, < 1.0, NAN,DOMAIN,EDOM
 acoshf, >=1.0, acosh(arg),,,

*/

/* 
 * wrapper acosh(x)
 */

#include "fdlibm.h"

#ifdef _LIBM_REENT
#define acosh _acosh_r
#endif

#if defined (_LIBM_REENT) || ! defined (_REENT_ONLY)

#ifdef __STDC__
	double acosh(_R1 double x)		/* wrapper acosh */
#else
	double acosh(_R2 x)			/* wrapper acosh */
	_R3 double x;
#endif
{
#ifndef _DOUBLE_IS_32BITS
#ifdef _IEEE_LIBM
	return __ieee754_acosh(x);
#else
	double z;
	z = __ieee754_acosh(x);
	if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
	if(x<1.0) {
	        return __kernel_standard(_R4,x,x,29); /* acosh(x<1) */
	} else
	    return z;
#endif
#else /* defined (_DOUBLE_IS_32BITS) */
	return (double) _acoshf_r (_R4, (float) x);
#endif /* defined (_DOUBLE_IS_32BITS) */
}

#endif /* defined (_LIBM_REENT) || ! defined (_REENT_ONLY) */