On Thu, Jun 23, 2016 at 01:22:55PM -0400, Andrei Alexandrescu via Digitalmars-d
wrote:
> So I was looking for an efficient exponentiation implementation, and
> http://www.stepanovpapers.com/PAM.pdf has a nice discussion starting
> at page 54. Stepanov's solution, however, duplicates code, so I
> eliminated it:
>
> https://dpaste.dzfl.pl/e53acb41885a
>
> The cost is the use of one goto. Can the code be restructured to not
> need it?
[...]
I don't understand why that goto is necessary. Or, indeed, why a nested
loop is needed at all. Why can't it be written like this?:
outer: for (;;)
{
if (e % 2 != 0)
{
r = mul(r, b, overflow);
if (e == 1) return r;
}
b = mul(b, b, overflow);
e /= 2;
}
AFAICT, the two possible code paths through the loops are the same. Am
I missing something??
T
--
Winners never quit, quitters never win. But those who never quit AND never win
are idiots.
