Implementation of a linear congruential generator.

lcg.js

/**
 * Implementation of a linear congruential generator.<br/>
 * The linear congruential generator follows this formula: x=(a*x+c)%n where a=multiplier, c=increment and m=modulus.<br/>
 * Multiplier, increment and modulus can be set separately or via one of the presets.<br/>
 * By default the Lehmer prng is used.
 * @summary Linear congruential generator
 */
var lcg = (function(){
	'use strict';
	var iMultiplier = 48271
		,iIncrement = 0
		,iModulus = 2147483647
		,iSeed = 123
		,oReturn = {
			rnd: rnd
			,random: random
			//
			,setMultiplier: setMultiplier
			,setIncrement: setIncrement
			,setModulus: setModulus
			//
			,getMultiplier: getMultiplier
			,getIncrement: getIncrement
			,getModulus: getModulus
			//
			,setSeed: setSeed
			//
			,presetLehmer: presetLehmer
			,presetJava: presetJava
			,presetNumeralRecipes: presetNumeralRecipes
		}
	;

	/**
	 * Returns a random number between zero and the set modulus
	 * @memberOf iddqd.math.prng.lcg
	 * @param {number} [seed] The seed from which to calculate
	 * @param {number} [iterate] The number of iterations
	 * @returns {number} An integer between zero and the set modulus
	 */
	function rnd(seed,iterate) {
		if (seed!==undefined) iSeed = seed;
		if (iterate===undefined) iterate = 1;
		while (iterate--) iSeed = (iMultiplier*iSeed+iIncrement)%iModulus;
		return iSeed;
	}

	/**
	 * Returns a random number between zero and one
	 * @memberOf iddqd.math.prng.lcg
	 * @param {number} [seed] The seed from which to calculate
	 * @param {number} [iterate] The number of iterations
	 * @returns {number} A floating point between zero and one
	 */
	function random(seed,iterate) {
		return rnd(seed,iterate)/iModulus;
	}

	/**
	 * @memberOf iddqd.math.prng.lcg
	 * @param {number} seed The integer seed
	 */
	function setSeed(seed) { iSeed = seed; }

	/**
	 * @memberOf iddqd.math.prng.lcg
	 * @param {number} multiplier The integer multiplier
	 */
	function setMultiplier(multiplier){	iMultiplier = multiplier; }

	/**
	 * @memberOf iddqd.math.prng.lcg
	 * @param {number} increment The integer increment
	 */
	function setIncrement(increment){	iIncrement = increment; }

	/**
	 * @memberOf iddqd.math.prng.lcg
	 * @param {number} modulus The integer modulus
	 */
	function setModulus(modulus){		iModulus = modulus; }

	/**
	 * @memberOf iddqd.math.prng.lcg
	 * @returns {number} The current multiplier
	 */
	function getMultiplier(){ return iMultiplier; }

	/**
	 * @memberOf iddqd.math.prng.lcg
	 * @returns {number} The current increment
	 */
	function getIncrement(){ return iIncrement; }

	/**
	 * @memberOf iddqd.math.prng.lcg
	 * @returns {number} The current modulus
	 */
	function getModulus(){ return iModulus; }

	/**
	 * Sets the current lcg settings to Lehmer
	 * @memberOf iddqd.math.prng.lcg
	 * @param {boolean} [minstd]
	 * @returns {iddqd.math.prng.lcg}
	 */
	function presetLehmer(minstd) {
		iMultiplier = minstd?16807:48271;
		iIncrement = 0;
		iModulus = 2147483647; // 2E31-1 mersenne prime
		return oReturn;
	}

	/**
	 * Sets the current lcg settings to Java
	 * @memberOf iddqd.math.prng.lcg
	 * @returns {iddqd.math.prng.lcg}
	 */
	function presetJava() {
		iMultiplier = 25214903917;
		iIncrement = 11;
		iModulus = 2E48;
		return oReturn;
	}

	/**
	 * Sets the current lcg settings to NumeralRecipes
	 * @memberOf iddqd.math.prng.lcg
	 * @returns {iddqd.math.prng.lcg}
	 */
	function presetNumeralRecipes() {
		iMultiplier = 1664525;
		iIncrement = 1013904223;
		iModulus = 2E32;
		return oReturn;
	}
	return oReturn;
})();