Complex, Rational, etc.

In addition to moving the Complex and Rational classes from stdlib to 
core, there seem to be a continuing series of related changes to the 
numeric classes.

I'd appreciate it if someone (do you read this list tadf?) could explain 
the big picture here.  What is the goal of these changes, and how are 
numbers changing in Ruby?

Here are some things I understand:

1) Complex and Rational are now in core and implemented in C, and so are 
presumably faster.

2) I still need to require complex.rb if I want Math methods to handle 
complex numbers.

3) Alternatively, I can require cmath.rb if I want CMath methods for 
complex numbers

Here are some things I have not figured out yet:

a) When should I include rational.rb?

b) Is mathn still useful?  Is it still supported?

c) What are the various ways to do division, and how do they differ?

d) Have these changes stabilized enough to document, or are things still 
likely to change?  For example is the name CMath official?

Thanks for any help!

	David Flanagan