Excerpts from Tom Nakamura's mail of 29 Apr 2005 (EDT):
> what features do a "properly embedded shell" have that a simple
> "screen"-split at console (or simply multiple windows open) do not?
> I'm not being sarcastic, i just want to know what i could be
> missing...

For languages with an interactive environment (like Ruby (irb) and R), a
good Emacs mode will let you run the environment in a split screen with
the code you're editing, and will make it easy to dump the current
line/selection/function into the environment.

I haven't figured out how to do this with Ruby yet, but with R I just
hit C-c M-f and whatever function the cursor is currently in gets dumped
into the interactive environment and evaluated. Makes debugging easy.

-- 
William <wmorgan-ruby-talk / masanjin.net>