Seeded random in Javascript, translated from Michael Baczynski's AS2 ( http://www.polygonal.de )

SeededRandomNumberGenerator.js

/*
 * Copyright (c) 2009 Michael Baczynski, http://www.polygonal.de
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/**
 * Implementation of the Park Miller (1988) "minimal standard" linear 
 * congruential pseudo-random number generator.
 * 
 * For a full explanation visit: http://www.firstpr.com.au/dsp/rand31/
 * 
 * The generator uses a modulus constant (m) of 2^31 - 1 which is a
 * Mersenne Prime number and a full-period-multiplier of 16807.
 * Output is a 31 bit unsigned integer. The range of values output is
 * 1 to 2,147,483,646 (2^31-1) and the seed must be in this range too.
 * 
 * David G. Carta's optimisation which needs only 32 bit integer math,
 * and no division is actually *slower* in flash (both AS2 & AS3) so
 * it's better to use the double-precision floating point version.
 * 
 * @author Michael Baczynski, www.polygonal.de

.............................................................................

 Converted to JavaScript by Lee Grey, Aug 3rd 2012
 
 */


/**
* set seed with a 31 bit unsigned integer
* between 1 and 0X7FFFFFFE inclusive. don't use 0!
*/


SeedRND = new SeededRandomNumberGenerator(); //global object

function SeededRandomNumberGenerator() {}

SeededRandomNumberGenerator.prototype.seed = 1337;

/**
* provides the next pseudorandom number
* as an unsigned integer (31 bits)
*/
SeededRandomNumberGenerator.prototype.randomInt = function()
{
	return this.gen();
}
	
/**
* provides the next pseudorandom number
* as a float between nearly 0 and nearly 1.0.
*/
SeededRandomNumberGenerator.prototype.random = function()
{
	return ( this.gen() / 2147483647 );
}
	
/**
* provides the next pseudorandom number
* as an unsigned integer (31 bits) betweeen
* a given range.
*/
SeededRandomNumberGenerator.prototype.randomIntRange = function(min, max)
{
	min -= .4999;
	max += .4999;
	return Math.round(min + ((max - min) * this.random()));
}
	
/**
* provides the next pseudorandom number
* as a float between a given range.
*/
SeededRandomNumberGenerator.prototype.randomRange = function(min, max)
{
	return min + ((max - min) * this.random());
}

/**
	* generator:
	* new-value = (old-value * 16807) mod (2^31 - 1)
	*/
SeededRandomNumberGenerator.prototype.gen = function()
{
	//integer version 1, for max int 2^46 - 1 or larger.
	return this.seed = (this.seed * 16807) % 2147483647;

	/**
		* integer version 2, for max int 2^31 - 1 (slowest)
		*/
	//var test:int = 16807 * (seed % 127773 >> 0) - 2836 * (seed / 127773 >> 0);
	//return seed = (test > 0 ? test : test + 2147483647);

	/**
		* david g. carta's optimisation is 15% slower than integer version 1
		*/
	//var hi:Number = 16807 * (seed >> 16);
	//var lo:Number = 16807 * (seed & 0xFFFF) + ((hi & 0x7FFF) << 16) + (hi >> 15);
	//return seed = (lo > 0x7FFFFFFF ? lo - 0x7FFFFFFF : lo);
}