A History Mechanism

Lisp-Stat uses the same history mechanism as Common Lisp. The symbols - + ++ +++ * ** *** have the following meaning:

-

The current input expression

+

The last expression read

++

The previous value of +

+++

The previous value of ++

*

The result of the last evaluation

**

The previous value of *

***

The previous value of ***

Thus

> (def x 1)
X
> (*)
1
> (/ * 10)
0.1
> (* * 10)
1.0
> (* ** 10)
1.0

Actually the first one is a trick. Notice that, for example, the symbol * can be both a function and a variable. If we ask for help about this symbol

> (help '*)
*                                                         [function-doc]
Args: (&rest numbers)
Returns the product of its arguments. With no args, returns 
1. Vectorized.
*                                                         [variable-doc]
The result of the last evaluation