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  ANSI Common Lisp   25 Environment   25.2 Dictionary of Environment

25.2.21 +, ++, +++ 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

Allegro CL Implementation Details:
None.

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