std.rational?

[bearophile]

Joseph Rushton Wakeling:

> Why was this never incorporated into Phobos?

First it needs the normal review process for Phobos modules :) It 
should go in the review queue, if it's good enough for Phobos.

> Rational!(BigInt) getTerm(int termNumber) {

I suggest to add inside that "rational.d" module an alias with 
Bigint, as:

alias Fraction = Rational!BigInt;

Because I don't think I want to use a rational type made with 
built-in integrals.

Bye,
bearophile