w_cosh.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_cosh.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
        <<cosh>>, <<coshf>>---hyperbolic cosine

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

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

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

DESCRIPTION

	<<cosh>> computes the hyperbolic cosine of the argument <[x]>.
	<<cosh(<[x]>)>> is defined as 
	@ifinfo
	. (exp(x) + exp(-x))/2
	@end ifinfo
	@tex
	$${(e^x + e^{-x})} \over 2$$
	@end tex

	Angles are specified in radians.  
		
	<<coshf>> is identical, save that it takes and returns <<float>>.

RETURNS
	The computed value is returned.  When the correct value would create
	an overflow,  <<cosh>> returns the value <<HUGE_VAL>> with the
	appropriate sign, and the global value <<errno>> is set to <<ERANGE>>.

	You can modify error handling for these functions using the
	function <<matherr>>.

PORTABILITY
	<<cosh>> is ANSI.  
	<<coshf>> is an extension.

QUICKREF
	cosh ansi pure
	coshf - pure
*/

/* 
 * wrapper cosh(x)
 */

#include "fdlibm.h"

#ifdef _LIBM_REENT
#define cosh _cosh_r
#endif

#if defined (_LIBM_REENT) || ! defined (_REENT_ONLY)
#ifdef __STDC__
	double cosh(_R1 double x)		/* wrapper cosh */
#else
	double cosh(_R2 x)			/* wrapper cosh */
	_R3 double x;
#endif
{
#ifndef _DOUBLE_IS_32BITS
#ifdef _IEEE_LIBM
	return __ieee754_cosh(x);
#else
	double z;
	z = __ieee754_cosh(x);
	if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
	if(fabs(x)>7.10475860073943863426e+02) {	
	        return __kernel_standard(_R4,x,x,5); /* cosh overflow */
	} else
	    return z;
#endif
#else /* defined (_DOUBLE_IS_32BITS) */
	return (double) _coshf_r (_R4, (float) x);
#endif /* defined (_DOUBLE_IS_32BITS) */
}

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