-a form.
20.2.0 6
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
+ (variable), * (variable), / (variable), Section 25.1.1 (Top level loop)
None.