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  ANSI Common Lisp   12 Numbers   12.2 Dictionary of Numbers

12.2.43 *random-state* Variable

Value Type:
a random state.

Initial Value:
implementation-dependent.

Description:
The current random state, which is used, for example, by the function random when a random state is not explicitly supplied.

Examples:
 (random-state-p *random-state*)  true
 (setq snap-shot (make-random-state))
 ;; The series from any given point is random,
 ;; but if you backtrack to that point, you get the same series.
 (list (loop for i from 1 to 10 collect (random))
       (let ((*random-state* snap-shot))
         (loop for i from 1 to 10 collect (random)))
       (loop for i from 1 to 10 collect (random))
       (let ((*random-state* snap-shot))
         (loop for i from 1 to 10 collect (random))))
 ((19 16 44 19 96 15 76 96 13 61)
    (19 16 44 19 96 15 76 96 13 61)
    (16 67 0 43 70 79 58 5 63 50)
    (16 67 0 43 70 79 58 5 63 50))

Affected By:
The implementation.

random.

See Also:
make-random-state, random, random-state

Notes:
Binding *random-state* to a different random state object correctly saves and restores the old random state object.

Allegro CL Implementation Details:
None.

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