/*
	log returns the natural logarithm of its floating
	point argument.

	The coefficients are #2705 from Hart & Cheney. (19.38D)

	It calls frexp.
*/

#include 
#include 

int	errno;
double	frexp();
static double	log2	= 0.693147180559945309e0;
static double	ln10	= 2.302585092994045684;
static double	sqrto2	= 0.707106781186547524e0;
static double	p0	= -.240139179559210510e2;
static double	p1	= 0.309572928215376501e2;
static double	p2	= -.963769093368686593e1;
static double	p3	= 0.421087371217979714e0;
static double	q0	= -.120069589779605255e2;
static double	q1	= 0.194809660700889731e2;
static double	q2	= -.891110902798312337e1;

double
log(arg)
double arg;
{
	double x,z, zsq, temp;
	int exp;

	if(arg <= 0.) {
		errno = EDOM;
		return(-HUGE);
	}
	x = frexp(arg,&exp);
	while(x<0.5) {
		x = x*2;
		exp = exp-1;
	}
	if(x
Назад