UpdateSeed (RandomNumberGenerator subroutine)

Reset random number object using specified Seed an

UpdateSeed is a member of the RandomNumberGenerator class.

This method sets a random number object to the number that would be created by the New constructor with the given Seed and Salt specifications.

Syntax

  %rand:UpdateSeed([Seed=seed] [, Salt=salt])

Syntax terms

%rand

A RandomNumberGenerator object variable.

Seed=seed

An optional, name required, argument that lets you specify a “seed” for the random number generator. If you provide no seed, the method generates a new, “random,” starting value for the random number generator. seed is a string or a longstring.

Salt=salt

An optional, name required, argument that lets you specify a “salt” for the random number generator. A salt is additional data to be used (along with the explicit or default seed) to improve the randomness of the random generator's initial value. salt is a string or a longstring.

Examples

In the following request, calling updateSeed enables the production of a second series of three values of %rand that matches the initial series of three values of %rand:

    begin
    %i is float
    %rand is object RandomNumberGenerator

    %rand = new(seed='help')
    for %i from 1 to 3
       printtext {~} = {%rand:value}
    end for

    %rand:updateSeed(seed='help')
    for %i from 1 to 3
       printtext {~} = {%rand:value}
    end for
    end

The result is:

    %rand:value = 816969049
    %rand:value = -148817379
    %rand:value = 895846046
    %rand:value = 816969049
    %rand:value = -148817379
    %rand:value = 895846046

If instead the random number is created with a salt, as in the following fragment, an updateSeed call using the salt produces a unique series of three values (salted numbers are not reproducible):

     ...
    %rand = new(salt='iou')
    for %i from 1 to 3
       printtext {~} = {%rand:value}
    end for

    %rand:updateSeed(salt='iou')
    for %i from 1 to 3
       printtext {~} = {%rand:value}
    end for

A sample result is:

    %rand:value = 320947512
    %rand:value = 535019615
    %rand:value = -526589924
    %rand:value = 387949238
    %rand:value = 413468100
    %rand:value = -807607538