Simple Middle Square Weyl Sequence PRNG

msws-common.js

/* Simple PRNG Based on https://en.wikipedia.org/wiki/Middle-square_method#Middle_Square_Weyl_Sequence_RNG
 *
 * Usage:
 *   node:
 *     var MSWS = require('msws.js');
 *
 *   browser:
 *     include this script in your html document
 *
 *   both:
 *     var prng = new MSWS();
 *
 *     var seed = prng.getSeed();
 *     prng.setSeet(seed);                                // static sequences
 *     //prng.setSeed(new Date().getTime());              // or randomize the seed
 *
 *     var min=0, max=1000, precision=3;
 *     console.log(prng.random());                        //    0f <=> 1f
 *     console.log(prng.getInt(max, min);                 //    0  <=> 1000
 *     console.log(prng.getFloat(max, min);               //    0f <=> 1000f
 *     console.log(prng.getFixed(precision, max, min);    // 0.000 <=> 1000.000
 */

(function() {
    var MSWS = (function() {
        var MSWS = function(opts) {
            this.x = 0;
            this.w = 0;
            this.s = opts && opts.seed || 0x45ad4ece;
            this.maxPrecision = opts && opts.maxPrecision || 10;
        };
        
        MSWS.prototype.getSeed = function() {
            return this.s;
        }
        
        MSWS.prototype.setSeed = function(seed) {
            this.s = seed;
        }
        
        MSWS.prototype.msws = function(max, min) {
            var clamped = !!max
              , done = false
              , i = 0
            ;
        
            max = max || 1;
            min = min || 0;
        
            while (!done) {
                i += 1;
        
                this.x *= this.x;
                this.x += (this.w += this.s);
                this.x = (this.x>>16) | (this.x<<16);
        
                this.x = (this.x < 0) ? this.x * -1 : this.x;
        
                var outOfBounds = clamped && ( (this.x > max) || (min && this.x < min) );
        
                if (!clamped) {
                    done = true;
        
                } else if (!outOfBounds) {
                    done = true;
                }
            }
        
            return this.x;
        }
        
        MSWS.prototype.getInt = function(max, min) {
            return this.msws(max, min);
        }
        
        MSWS.prototype.getFloat = function(max, min) {
            min = min || 0;
            max = max || 1;
        
            var whole = (max === 1) ? 0 : this.getInt(max-1, min)
              , part = this.getInt(+'1'+'0'.repeat(this.maxPrecision))
              , result = +whole + '.' + part
            ;
        
            return result;
        }
        
        MSWS.prototype.getFixed = function(precision, max, min) {
            precision = precision || 2;
            min = min || 0;
            max = max || 1;

            precision = precision >= this.maxPrecision ? this.maxPrecision : precision;
            return new Number(this.getFloat(max, min)).toFixed(precision);
        }

        MSWS.prototype.random = function() {
            return this.getFloat(1, 0);
        }

        return MSWS;
    })();

    if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
        module.exports = MSWS
    } else {
        window.MSWS = MSWS
    }
})();

msws-es6.js

/*  See sample-es6.js for usage

    Note: es6 module import / export not available in node; issues summarized at
    https://medium.com/the-node-js-collection/an-update-on-es6-modules-in-node-js-42c958b890c

export default class MSWS {

    use commonjs instead
*/

module.exports = class MSWS {
    constructor(opts) {
        this.x = 0;
        this.w = 0;
        this.s = opts && opts.seed || 0;
        this.maxPrecision = opts && opts.maxPrecision || 10;
    }

    getSeed() {
        return this.s;
    }

    setSeed(seed) {
        this.s = seed;
    }

    getInt(max = 1, min = 0) {
        return this._msws(max, min);
    }

    getFloat(max = 1, min = 0) {
        let whole = (max === 1) ? 0 : this.getInt(max - 1, min)
          , part = this.getInt(+'1' + ('0'.repeat(this.maxPrecision)))
          , result = +whole + '.' + part
        ;

        return result;
    }

    getFixed(precision = 2, max = 1, min = 0) {
        precision = precision >= this.maxPrecision ? this.maxPrecision : precision;
        return new Number(this.getFloat(max, min)).toFixed(precision);
    }
  
    random(max = 1, min = 0) {
        return this.getFloat(max, min);
    }

    _msws(max = 1, min = 0) {
        let clamped = !!max
          , done = false
          , i = 0
        ;

        while (!done) {
            i += 1;

            this.x *= this.x;
            this.x += (this.w += this.s);
            this.x = (this.x>>16) | (this.x<<16);

            this.x = (this.x < 0) ? this.x * -1 : this.x;

            let outOfBounds = clamped && ( (this.x > max) || (min && this.x < min) );

            if (!clamped) {
                done = true;

            } else if (!outOfBounds) {
                done = true;
            }
        }

        return this.x;
    }

    // cannot be called by instance
    static versionInfo() {
        let version = 1

        return `MSWS, a Middle Square Weyl Sequence prng.\nversion ${version.toFixed(2)}\n`;

    }
}

sample-es6.js

/*  Note: es6 module import / export not available in node; issues summarized at
    https://medium.com/the-node-js-collection/an-update-on-es6-modules-in-node-js-42c958b890c

import MSWS from 'msws';

    use commonjs instead
*/

let MSWS = require('./msws')
  , prng = new MSWS({ seed: 3 })
;

console.log("%s", MSWS.versionInfo());

// integers
for (let i=0; i<10; i++) {
    console.log("getInt(10): %d", prng.getInt(10));
}

// floats
console.log("\ngetFloat(): %s", prng.getFloat());
console.log("getFloat(100, 90): %s", prng.getFloat(100, 90));

// fixed-precision
console.log("\ngetFixed():   %s", prng.getFixed());
console.log("getFixed(4):  %s", prng.getFixed(4));
console.log("getFixed(6):  %s", prng.getFixed(6));
console.log("getFixed(8):  %s", prng.getFixed(8));
console.log("getFixed(10): %s", prng.getFixed(10));

// random
console.log("\nrandom(): %s", prng.random());