Отправлено гоша 01 июня 2004 г. 11:25 В ответ на: Может быть у кого есть готовая программа извлечения квадратного корня для МЕГИ (AVR)? отправлено Designer 01 июня 2004 г. 10:35

#include	
double
sqrt(x)
double	x;
{
	double	og, ng;
	short	niter;
	int	expon;
	if(x <= 0.0)
		return 0.0;
	og = x;
	if(og < 1.0)
		og = 1.0/og;
	og = frexp(og, &expon);
	og = ldexp(og, expon/2);		/* make an educated guess */
	if(x < 1.0)
		og = 1.0/og;
	niter = 20;
	do {
		ng = (x/og + og)/2.0;
		if(ng == og)
			break;
		og = ng;
	} while(--niter);
	return og;
}
/*	Frexp/ldexp in C 
/*
 *	$Header: /hitech/cvsroot/nz/libc/common/frexp.c,v 1.4 2003/07/25 01:23:21 lucky Exp $
 *
 *	$Log: frexp.c,v $
 *	Revision 1.4  2003/07/25 01:23:21  lucky
 *	Changed MSP's macro to __MSP430C__
 *	
 *	Revision 1.3  2002/12/19 03:49:25  clyde
 *	Added MSP430 to frexp.c
 *	
 *	Revision 1.2  1995/10/18 15:36:10  clyde
 *	64 bit mods
 *	
 * Revision 1.1  95/10/08  22:00:28  clyde
 * Initial revision
 * 
 * Revision 1.1  95/10/08  21:59:28  clyde
 * Initial revision
 * 
 */
#if	defined(_XA_) || defined(i8096) || defined(i8086) || defined(__MSP430C__)
#define	LITTLE_ENDIAN
#endif
#if	sizeof(double) == 4
union both
{
	struct flt
	{
#if	z80
#define	EXCESS	64
		unsigned char	mant[2];
		unsigned	hmant:8;
		unsigned	exp:7;
		unsigned	sign:1;
#else
#define	EXCESS	126
#ifdef	LITTLE_ENDIAN
		unsigned char	mant[2];
		unsigned	hmant:7;
		unsigned	exp:8;
		unsigned	sign:1;
#else
		unsigned	sign:1;
		unsigned	exp:8;
		unsigned	hmant:7;
		unsigned char	mant[2];
#endif
#endif
	}	flt;
	double	fl;
};
#else	
#define	EXCESS	1022
union both
{
	struct flt
	{
#ifdef	LITTLE_ENDIAN
		unsigned char	mant[6];
		unsigned	hmant:4;
		unsigned	exp:11;
		unsigned	sign:1;
#else
		unsigned	sign:1;
		unsigned	exp:11;
		unsigned	hmant:4;
		unsigned char	mant[6];
#endif
	}	flt;
	double	fl;
};
#endif
double
frexp(union both value, int * eptr)
{
	*eptr = value.flt.exp - EXCESS;
	value.flt.exp = EXCESS;
	return value.fl;
}
double
ldexp(union both value, int newexp)
{
	value.flt.exp += newexp;
	return value.fl;
}