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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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