@syntest/prng
Version:
The pseudo random number generator library of the SynTest Framework
92 lines • 3.57 kB
JavaScript
;
/*
* Copyright 2020-2021 Delft University of Technology and SynTest contributors
*
* This file is part of SynTest Framework - SynTest Core.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
Object.defineProperty(exports, "__esModule", { value: true });
exports.prng = exports.initializePseudoRandomNumberGenerator = void 0;
const bignumber_js_1 = require("bignumber.js");
const seedrandom = require("seedrandom");
const Charset_1 = require("./Charset");
const diagnostics_1 = require("./diagnostics");
let random;
function initializePseudoRandomNumberGenerator(seed) {
if (random) {
throw new Error((0, diagnostics_1.singletonAlreadySet)("PseudoRandomNumberGenerator"));
}
random = seedrandom(seed);
Math.random = random;
}
exports.initializePseudoRandomNumberGenerator = initializePseudoRandomNumberGenerator;
function generator() {
if (!random) {
throw new Error((0, diagnostics_1.singletonNotSet)("PseudoRandomNumberGenerator"));
}
return random();
}
/**
* The global random generator.
*/
exports.prng = {
nextBoolean: (trueChance = 0.5) => {
return generator() <= trueChance;
},
nextInt: (min = 0, max = Number.MAX_SAFE_INTEGER) => {
const value = generator();
return Math.round(value * (max - min)) + min;
},
nextBigInt: (min = new bignumber_js_1.default(0), max = new bignumber_js_1.default(Number.MAX_SAFE_INTEGER)) => {
const value = new bignumber_js_1.default(generator());
return value.multipliedBy(max.minus(min)).plus(min).integerValue();
},
nextDouble: (min = 0, max = Number.MAX_SAFE_INTEGER) => {
const value = generator();
return value * (max - min) + min;
},
nextBigDouble: (min = new bignumber_js_1.default(0), max = new bignumber_js_1.default(Number.MAX_SAFE_INTEGER)) => {
const value = new bignumber_js_1.default(generator());
return value.multipliedBy(max.minus(min)).plus(min);
},
/**
* Uses the Box-Muller transform to get a gaussian random variable.
*
* Based on:
* https://en.wikipedia.org/wiki/Box%E2%80%93Muller_transform
*/
nextGaussian: (mu = 0, sigma = 1) => {
const u1 = generator();
const u2 = generator();
const mag = sigma * Math.sqrt(-2 * Math.log(u1));
return mag * Math.cos(2 * Math.PI * u2) + mu;
},
pickOne: (options) => {
if (options.length === 0) {
throw new Error((0, diagnostics_1.emptyArray)("options"));
}
const value = generator();
const index = Math.round(value * (options.length - 1));
return options[index];
},
uniqueId: (length = 7, characters = Charset_1.Charset.alpha + Charset_1.Charset.alphaCapital) => {
const charactersLength = characters.length;
let result = "";
for (let index = 0; index < length; index++) {
result += characters.charAt(Math.floor(generator() * charactersLength));
}
return result;
},
};
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