newlib-cygwin/newlib/libm/common/s_isnan.c

/* @(#)s_isnan.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
	<<isnan>>, <<isnanf>>, <<isinf>>, <<isinff>>, <<finite>>, <<finitef>>---test for exceptional numbers

INDEX
	isnan
INDEX
	isinf
INDEX
	finite

INDEX
	isnanf
INDEX
	isinff
INDEX
	finitef

ANSI_SYNOPSIS
	#include <ieeefp.h>
	int isnan(double <[arg]>);
	int isinf(double <[arg]>);
	int finite(double <[arg]>);
	int isnanf(float <[arg]>);
	int isinff(float <[arg]>);
	int finitef(float <[arg]>);

TRAD_SYNOPSIS
	#include <ieeefp.h>
	int isnan(<[arg]>)
	double <[arg]>;
	int isinf(<[arg]>)
	double <[arg]>;
	int finite(<[arg]>);
	double <[arg]>;
	int isnanf(<[arg]>);
	float <[arg]>;
	int isinff(<[arg]>);
	float <[arg]>;
	int finitef(<[arg]>);
	float <[arg]>;


DESCRIPTION
	These functions provide information on the floating-point
	argument supplied.

	There are five major number formats:
	o+
	o zero
	  A number which contains all zero bits.
	o subnormal
	  A number with a zero exponent but a nonzero fraction.
	o normal
	  A number with an exponent and a fraction.
     	o infinity
	  A number with an all 1's exponent and a zero fraction.
	o NAN
	  A number with an all 1's exponent and a nonzero fraction.

	o-

	<<isnan>> returns 1 if the argument is a nan. <<isinf>>
	returns 1 if the argument is infinity.  <<finite>> returns 1 if the
	argument is zero, subnormal or normal.
	
	The <<isnanf>>, <<isinff>> and <<finitef>> functions perform the same
	operations as their <<isnan>>, <<isinf>> and <<finite>>
	counterparts, but on single-precision floating-point numbers.

	It should be noted that the C99 standard dictates that <<isnan>>
	and <<isinf>> are macros that operate on multiple types of
	floating-point.  The SUSv2 standard declares <<isnan>> as
	a function taking double.  Newlib has decided to declare
	them both as macros in math.h and as functions in ieeefp.h.

QUICKREF
	isnan - pure
QUICKREF
	isinf - pure
QUICKREF
	finite - pure
QUICKREF
	isnan - pure
QUICKREF
	isinf - pure
QUICKREF
	finite - pure
*/

/*
 * isnan(x) returns 1 is x is nan, else 0;
 * no branching!
 *
 * The C99 standard dictates that isnan is a macro taking
 * multiple floating-point types while the SUSv2 standard
 * notes it is a function taking a double argument.  Newlib
 * has chosen to implement it as a macro in <math.h> and
 * declare it as a function in <ieeefp.h>.
 */

#include "fdlibm.h"
#include <ieeefp.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
	int isnan(double x)
#else
	int isnan(x)
	double x;
#endif
{
	__int32_t hx,lx;
	EXTRACT_WORDS(hx,lx,x);
	hx &= 0x7fffffff;
	hx |= (__uint32_t)(lx|(-lx))>>31;	
	hx = 0x7ff00000 - hx;
	return (int)(((__uint32_t)(hx))>>31);
}

#endif /* _DOUBLE_IS_32BITS */