CLHS: Variable *RANDOM-STATE*

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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.

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.

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