+, ++, +++
+, ++, +++ Variable
Value Type:
an object.
Initial Value:
implementation-dependent.
Description:
The variables +, ++, and +++ are maintained by the Lisp read-eval-print loop to save forms that were recently evaluated.
The value of + is the last form that was evaluated, the value of ++ is the previous value of +, and the value of +++ is the previous value of ++.
Examples:
(+ 0 1) → 1
(- 4 2) → 2
(/ 9 3) → 3
(list + ++ +++) → ((/ 9 3) (- 4 2) (+ 0 1))
(setq a 1 b 2 c 3 d (list a b c)) → (1 2 3)
(setq a 4 b 5 c 6 d (list a b c)) → (4 5 6)
(list a b c) → (4 5 6)
(eval +++) → (1 2 3)
#.‘(,@++ d) → (1 2 3 (1 2 3))
Affected By:
Lisp read-eval-print loop.
See Also:
- (variable), * (variable), / (variable), Section 25.1.1 (Top level loop)
∗**,** ∗∗**,** ∗∗∗ Variable
Value Type:
an object.
Initial Value:
implementation-dependent.
Description:
The variables *, **, and *** are maintained by the Lisp read-eval-print loop to save the values of results that are printed each time through the loop.
The value of * is the most recent primary value that was printed, the value of ** is the previous value of *, and the value of *** is the previous value of **.
If several values are produced, * contains the first value only; * contains nil if zero values are produced.
The values of *, **, and *** are updated immediately prior to printing the return value of a top-level form by the Lisp read-eval-print loop. If the evaluation of such a form is aborted prior to its normal return, the values of *, **, and *** are not updated.
Examples:
(values ’a1 ’a2) → A1, A2
’b → B
(values ’c1 ’c2 ’c3) → C1, C2, C3
(list \* \*\* \*\*\*) → (C1 B A1)
(defun cube-root (x) (expt x 1/3)) → CUBE-ROOT
(compile \*) → CUBE-ROOT
(setq a (cube-root 27.0)) → 3.0
(\* \* 9.0) → 27.0
Affected By:
Lisp read-eval-print loop.
See Also:
- (variable), + (variable), / (variable), Section 25.1.1 (Top level loop)
Notes:
* ≡ (car /)
** ≡ (car //)
*** ≡ (car ///)
Expanded Reference: +, ++, +++
TODO: Please contribute to this page by adding explanations and examples
(+, ++, +++ )