What is the mode for displaying auto-updating values of s-expressions in an emacs-lisp buffer?

Question

There is a mode for emacs-lisp buffers which allows one to display the value of each expression line by line, and updates the value of the expressions as soon as these are edited. It looks something like:

(+ 1 1) -> 2

(* 2 3) -> 6

What is the name of this mode? I have seen it in action and used it but I have forgotten how it is invoked.

Answer 1

I think you're looking for litable, which is a reimplementation of the corresponding LightTable feature.

Answer 2

I think you are referring to lively.el. Download the file, load it into Emacs and execute with M-x lively on the file. You will see this information periodically updated:

;;;   Current time:      (current-time-string)
;;;   Last command:      last-command
;;;   Open buffers:      (length (buffer-list))
;;;   Unix processes:    (lively-shell-command "ps -a | wc -l")