usr/src/usr.bin/f77/libF77/pow_ii.c

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *
 *	@(#)pow_ii.c	5.3	%G%
 *
 *  Corrections by Robert P. Corbett, 1983 March 2
 *  Revised to restore portability, 1983 March 4
 */


long int pow_ii(ap, bp)
long int *ap, *bp;
{
	long int pow, x, n;

	pow = 1;
	x = *ap;
	n = *bp;

	if (n == 0)
		return ( 1L );

	if (x == 0)
	{
		if( n > 0 )
			return ( 0L );
		else
			return ( 1/x );
	}

	if (x == 1)
		return ( 1L );

	if (x == -1)
	{
		if (n < 0)
		{
			if (n < -2)
				n += 2;
			n = -n;
		}
		if (n % 2 == 0)
			return ( 1L );
		else
			return ( -1L );
	}

	if (n > 0)
		for( ; ; )
		{
			if(n & 01)
				pow *= x;
			if(n >>= 1)
				x *= x;
			else
				break;
		}
	else
		pow = 0;

	return(pow);
}
Commit	Line	Data
	1	/*
	2	* Copyright (c) 1980 Regents of the University of California.
	3	* All rights reserved. The Berkeley software License Agreement
	4	* specifies the terms and conditions for redistribution.
	5	*
	6	* @(#)pow_ii.c 5.3 %G%
	7	*
	8	* Corrections by Robert P. Corbett, 1983 March 2
	9	* Revised to restore portability, 1983 March 4
	10	*/
	11
	12
	13	long int pow_ii(ap, bp)
	14	long int ap, bp;
	15	{
	16	long int pow, x, n;
	17
	18	pow = 1;
	19	x = *ap;
	20	n = *bp;
	21
	22	if (n == 0)
	23	return ( 1L );
	24
	25	if (x == 0)
	26	{
	27	if( n > 0 )
	28	return ( 0L );
	29	else
	30	return ( 1/x );
	31	}
	32
	33	if (x == 1)
	34	return ( 1L );
	35
	36	if (x == -1)
	37	{
	38	if (n < 0)
	39	{
	40	if (n < -2)
	41	n += 2;
	42	n = -n;
	43	}
	44	if (n % 2 == 0)
	45	return ( 1L );
	46	else
	47	return ( -1L );
	48	}
	49
	50	if (n > 0)
	51	for( ; ; )
	52	{
	53	if(n & 01)
	54	pow *= x;
	55	if(n >>= 1)
	56	x *= x;
	57	else
	58	break;
	59	}
	60	else
	61	pow = 0;
	62
	63	return(pow);
	64	}