On 2013-09-20 18:31, Brandon Allbery wrote:
[--snip--]

> unless you have a very clever representation that can store
> in terms of some operation like sin(x) or ln(x).)

I may just be hallucinating, but I think this is called "describable
numbers", i.e. numbers which can described by some (finite) formula.

Not sure how useful they would be in practice, though :).