make-random-state

ToC

Allegro CL

ANSI Common Lisp

12 Numbers

12.2 Dictionary of Numbers

12.2.40 make-random-state

Function

Syntax:

make-random-state &optional state

new-state

Arguments and Values:

state - a random state, or nil, or t. The default is nil.

new-state - a random state object.

Description:

Creates a fresh object of type random-state suitable for use as the value of *random-state*.

If state is a random state object, the new-state is a copy₅ of that object. If state is nil, the new-state is a copy₅ of the current random state. If state is t, the new-state is a fresh random state object that has been randomly initialized by some means.

Examples:

 (let* ((rs1 (make-random-state nil))
        (rs2 (make-random-state t))
        (rs3 (make-random-state rs2))
        (rs4 nil))
   (list (loop for i from 1 to 10 
               collect (random 100)
               when (= i 5)
                do (setq rs4 (make-random-state)))
         (loop for i from 1 to 10 collect (random 100 rs1))
         (loop for i from 1 to 10 collect (random 100 rs2))
         (loop for i from 1 to 10 collect (random 100 rs3))
         (loop for i from 1 to 10 collect (random 100 rs4))))
 ((29 25 72 57 55 68 24 35 54 65)
    (29 25 72 57 55 68 24 35 54 65)
    (93 85 53 99 58 62 2 23 23 59)
    (93 85 53 99 58 62 2 23 23 59)
    (68 24 35 54 65 54 55 50 59 49))

Exceptional Situations:

Should signal an error of type type-error if state is not a random state, or nil, or t.

See Also:

random, *random-state*

Notes:

One important use of make-random-state is to allow the same series of pseudo-random numbers to be generated many times within a single program.

Allegro CL Implementation Details:

See cl:random and cl:make-random-state for information on the Allegro CL implementation of make-random-state. Note the links are to the documentation for the current Allegro CL version. Replace /current/ in the URL with the Allegro CL version number to see similar documentation in earlier releases.