Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!hp4nl!philapd!ssp9!dolf
From: dolf@idca.tds.PHILIPS.nl (Dolf Grunbauer)
Newsgroups: comp.lang.c
Subject: Re: # to the nth power
Message-ID: <522@ssp9.idca.tds.philips.nl>
Date: 2 Nov 90 08:23:08 GMT
References: <90305.005050CJH101@psuvm.psu.edu-> <15984@mentor.cc.purdue.edu-> <9750@helios.TAMU.EDU> <1990Nov1.232830.17131@NCoast.ORG>
Reply-To: dolf@idca.tds.philips.nl (Dolf Grunbauer)
Organization: Philips Information Systems, Apeldoorn, The Netherlands
Lines: 37

In article <1990Nov1.232830.17131@NCoast.ORG> catfood@NCoast.ORG (Mark W. Schumann) writes:
<int powi (int root, int exponent)
<{
<int i;
<int result = 1;
<  for (i = exponent; i > 1; i--) result *= root;
Oeps, I think this one ---^ should be a 0

<  return result;
<  }

A quicker version (throw in a few registers if still not fast enough):
int powi (int root, int exponent)
{
   int result = 1;

   while (exponent > 0)
   {
      while (!(exponent & 1))
      {
         root     *= root;
         exponent /= 2;
      }
      result *= root;
      exponent--;
   }

   return result;
}
<Now you've gotta be careful about overflow here or use long ints.
<If you needed an integer version I hope this helps.
This is still true for my version as well, and also exponent must be >= 0;
-- 
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