a form.
implementation-dependent.
The value of - is the form that is currently being evaluated by the Lisp read-eval-print loop.
(format t "~&Evaluating ~S~
|>
Evaluating (FORMAT T "~&Evaluating ~S~
⇒ NIL
Lisp read-eval-print loop.
+ (variable), * (variable), / [Function] (variable), Top level loop