# to the nth power

[Mark W. Schumann]

In article <522 at ssp9.idca.tds.philips.nl> dolf at idca.tds.philips.nl (Dolf Grunbauer) writes:

> [I had written]:
>int powi (int root, int exponent)
>{
>int i;
>int result = 1;
>  for (i = exponent; i > 1; i--) result *= root;

Dolf says:

>Oeps, I think this one ---^ should be a 0

Nope.  I intended to leave out the iteration where you'd only be multiplying
by one.

>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;
>}

Spiffy, but it does depend on (exponent & 1) being the same as saying
"exponent is odd."  Most implementations support this, though.
Again, neither solution supports negative exponents.

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