4.3BSD - /usr/src/usr.lib/libF77/pow_hh.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_hh.c	5.2	6/26/85
   7:  */
   8: 
   9: short pow_hh(ap, bp)
  10: short *ap, *bp;
  11: {
  12:     short int pow, x, n;
  13: 
  14:     pow = 1;
  15:     x = *ap;
  16:     n = *bp;
  17: 
  18:     if (n == 0)
  19:         return ( 1L );
  20: 
  21:     if (x == 0)
  22:     {
  23:         if( n > 0 )
  24:             return ( 0L );
  25:         else
  26:             return ( 1/x );
  27:     }
  28: 
  29:     if (x == 1)
  30:         return ( 1L );
  31: 
  32:     if (x == -1)
  33:     {
  34:         if (n < 0)
  35:         {
  36:             if (n < -2)
  37:                 n += 2;
  38:             n = -n;
  39:         }
  40:         if (n % 2 == 0)
  41:             return ( 1L );
  42:         else
  43:             return ( -1L );
  44:     }
  45: 
  46:     if (n > 0)
  47:         for( ; ; )
  48:         {
  49:             if(n & 01)
  50:                 pow *= x;
  51:             if(n >>= 1)
  52:                 x *= x;
  53:             else
  54:                 break;
  55:         }
  56:     else
  57:         pow = 0;
  58: 
  59:     return(pow);
  60: }

Defined functions