UpdateSeed (RandomNumberGenerator subroutine): Difference between revisions

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This method sets a random number object to the number
This method sets a random number object to the number
that would be created by the [[New (RandomNumberGenerator constructor)|New constructor]]
that would be created by the <var>[[New (RandomNumberGenerator constructor)|New]]</var> <var>Constructor</var>
with the given Seed and Salt specifications.
with the given <var>Seed</var> and <var>Salt</var> parameter specifications.
 
==Syntax==
==Syntax==
{{Template:RandomNumberGenerator:UpdateSeed syntax}}
{{Template:RandomNumberGenerator:UpdateSeed syntax}}
===Syntax terms===
===Syntax terms===
<table class="syntaxTable">
<table class="syntaxTable">
<tr><th>randomNumberGenerator</th>
<tr><th>randomNumberGenerator</th>
<td>A <var>RandomNumberGenerator</var> object variable. </td></tr>
<td>A <var>RandomNumberGenerator</var> object variable. </td></tr>
<tr><th><var>Seed</var></th>
<tr><th><var>Seed</var></th>
<td>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.
<td>An optional, [[Notation conventions for methods#Named parameters|name required]], string 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.</td></tr>


<var>Seed</var> is a string. </td></tr>
<tr><th><var>Salt</var></th>
<tr><th><var>Salt</var></th>
<td>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.
<td>An optional, name required, string 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.
 
</td></tr>
<var>salt</var> is a string.</td></tr>
 
</table>
</table>


==Examples==
==Examples==
 
In the following request, calling <var>UpdateSeed</var> enables the production of a second
In the following request, calling updateSeed enables the production of a second
series of three values of <code>%rand</code> that matches the initial series of three
series of three values of %rand that matches the initial series of three
values of <code>%rand</code>:
values of %rand:
<p class="code">begin
<p class="code">begin
%i is float
%i is float
Line 53: Line 52:
If instead the random number is created with a salt,
If instead the random number is created with a salt,
as in the following fragment,
as in the following fragment,
an updateSeed call using the salt produces a unique series of
an <var>UpdateSeed</var> call using the salt produces a unique series of
three values (salted numbers are not reproducible):
three values (salted numbers are not reproducible):
<p class="code">...
<p class="code">...

Latest revision as of 21:35, 6 November 2012

Reset random sequence with new salt and seed (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 parameter specifications.

Syntax

randomNumberGenerator:UpdateSeed[( [Seed= string], [Salt= string])]

Syntax terms

randomNumberGenerator A RandomNumberGenerator object variable.
Seed An optional, name required, string 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.
Salt An optional, name required, string 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.

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

See also