BSD 4_4 release

[unix-history] / usr / src / usr.bin / f77 / libF77 / pow_ii.c

/*-
* Copyright (c) 1980 The Regents of the University of California.
* All rights reserved.
*
* This module is believed to contain source code proprietary to AT&T.
* Use and redistribution is subject to the Berkeley Software License
* Agreement and your Software Agreement with AT&T (Western Electric).
*/

#ifndef lint
static char sccsid[] = "@(#)pow_ii.c    5.4 (Berkeley) 4/12/91";
#endif /* not lint */

/*  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);
}