Anything in the review queue?

[dsimcha]

== Quote from Don (nospam at nospam.com)'s article
> > Ok, I don't know much about how BigInts work under the hood.  I used a
> > fairly simple implementation of Euler's algorithm here.  Is there
> > something much more efficient for BigInts?
> Yes. Euler's algorithm performs very poorly for BigInts. In fact, you
> probably want to use the BinaryGCD algorithm even for builtins.
> There is a sub-quadratic algorithm for GCD, but it's very complicated.
> (It's not the one Kenny posted).
> >> I guess the primary question is:
> >> If there were a BigRational type, would you still want rational?
> >> Ie, are there use cases for rational over built-in types (rather than it
> >> just being a workaround for a lack of a BigRational type)?
> >
> > My thoughts were that Rational would be **primarily** used with BigInt,
> > but occasionally, if you really know what you're doing with regard to
> > overflow, you could used fixed width as an optimization.
> This isn't sounding so promising.
> I hate to be saying that.

I've thought about this some more.  The following **may** be a good way to
proceed.  I'd like Don's input, since I don't know in detail what he was planning.

1.  Review the design of my rational lib with a focus on whether sufficient
infrastructure for creating specializations without introducing breaking changes
is available.

2.  If no issues not related to the lack of specialization for BigInt are raised,
accept Rational into Phobos for now.

3.  At his leisure, Don can write a specialization of Rational specifically for
BigInt (or even just a specialization of gcd, if that's all that's needed).  Once
this is done, we include it as an optimization, but without changes to the
interface.  Every integer type except BigInt still uses the generic implementation.

4.  Maybe we provide hooks for specializing certain performance-critical things
like GCD, in case someone wants to use their own custom BigInt type with Rational
without having to modify the code for Phobos.  For example, a BigInt type might
optionally define a gcd() method.  Rational would look for this and use it if it
exists, or use the generic fallback algorithm otherwise.