4.3BSD - /usr/src/usr.lib/libF77/pow_ii.c

   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	6/26/85
   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: }

Defined functions