random-state

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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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