[unix-history] / usr / src / lib / libc / gen / frexp.c

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)frexp.c	5.3 (Berkeley) %G%";
#endif LIBC_SCCS and not lint

#include <math.h>

/*
 *	the call
 *		x = frexp(arg,&exp);
 *	must return a double fp quantity x which is <1.0
 *	and the corresponding binary exponent "exp".
 *	such that
 *		arg = x*2^exp
 *	if the argument is 0.0, return 0.0 mantissa and 0 exponent.
 */

double
frexp(x,i)
double x;
int *i;
{
	int neg;
	int j;
	j = 0;
	neg = 0;
	if(x<0){
		x = -x;
		neg = 1;
		}
	if(x>=1.0)
		while(x>=1.0){
			j = j+1;
			x = x/2;
			}
	else if(x<0.5 && x != 0.0)
		while(x<0.5){
			j = j-1;
			x = 2*x;
			}
	*i = j;
	if(neg) x = -x;
	return(x);
	}
Commit	Line	Data
2ce81398	1	#if defined(LIBC_SCCS) && !defined(lint)
c5980113	2	static char sccsid[] = "@(#)frexp.c 5.3 (Berkeley) %G%";
2ce81398	3	#endif LIBC_SCCS and not lint
b8f253e8	4
c5980113 DS	5	#include <math.h>
c5980113 DS	6
29aaea38	7	/*
b8f253e8 KM	8	* the call
	9	* x = frexp(arg,&exp);
	10	* must return a double fp quantity x which is <1.0
	11	* and the corresponding binary exponent "exp".
	12	* such that
	13	* arg = x*2^exp
	14	* if the argument is 0.0, return 0.0 mantissa and 0 exponent.
	15	*/
29aaea38 BJ	16
	17	double
	18	frexp(x,i)
	19	double x;
	20	int *i;
	21	{
	22	int neg;
	23	int j;
	24	j = 0;
	25	neg = 0;
	26	if(x<0){
	27	x = -x;
	28	neg = 1;
	29	}
be56fc55 RC	30	if(x>=1.0)
be56fc55 RC	31	while(x>=1.0){
29aaea38 BJ	32	j = j+1;
	33	x = x/2;
	34	}
be56fc55	35	else if(x<0.5 && x != 0.0)
29aaea38 BJ	36	while(x<0.5){
	37	j = j-1;
	38	x = 2*x;
	39	}
	40	*i = j;
	41	if(neg) x = -x;
	42	return(x);
	43	}