Are the variables *,+, and / bound to recent input in SLIME or Clozure CL?

Question

I was messing around in SLIME (connected a Clozure REPL) when I discovered this:

It looks like the variables +, *, and / are all bound to some variation on recent input, + is the input itself, * is the result of evaluating that input, and / is the result contained in a list.

Is this right? Who is responsible for this, SLIME or Clozure? I couldn't find anything in the SLIME manual.

Thanks!

; SLIME 2010-05-13
CL-USER> +
NIL
CL-USER> *
NIL
CL-USER> /
(NIL)
CL-USER> -
-
CL-USER> +
-
CL-USER> (list 1 2)
(1 2)
CL-USER> +
(LIST 1 2)
CL-USER> /
((LIST 1 2))
CL-USER> (+ 1 2)
3
CL-USER> /
(3)
CL-USER> *
(3)
CL-USER> (* 1 2)
2
CL-USER> *
2
CL-USER> 

Answer 1

Those are all, and more, specified by the Common Lisp standard. Search the environment dictionary for 'Variable'.

Answer 2

+
++
+++

While a form is being evaluated by the top-level loop, the variable + is bound to the previous form read by the loop. The variable ++ holds the previous value of + (that is, the form evaluated two interactions ago), and +++ holds the previous value of ++.

-

While a form is being evaluated by the top-level loop, the variable - is bound to the form itself; that is, it is the value about to be given to + once this interaction is done.

*
**
***

While a form is being evaluated by the top-level loop, the variable * is bound to the result printed at the end of the last time through the loop; that is, it is the value produced by evaluating the form in +. If several values were produced, * contains the first value only; * contains nil if zero values were produced. The variable ** holds the previous value of * (that is, the result printed two interactions ago), and * holds the previous value of **.

/
//
///

While a form is being evaluated by the top-level loop, the variable / is bound to a list of the results printed at the end of the last time through the loop; that is, it is a list of all values produced by evaluating the form in +. The value of * should always be the same as the car of the value of /. The variable // holds the previous value of / (that is, the results printed two interactions ago), and /// holds the previous value of //. Therefore the value of ** should always be the same as the car of //, and similarly for * and ///.

From Common Lisp the Language, 2nd Edition 20.2