CLCS
Variable

*random-state*

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.

Notes

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