// This is part of Leandro Motta Barros' DUMP project
// http://stackedboxes.org/2020/01/05/dump-of-unsorted-morsels-for-programmers/
// Code is licensed under the MIT license
//
//
// Copyright 2017-2020 Leandro Motta Barros
//
// 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.

function boxMullerTransform(u0: number, u1: number): [number, number] {
    let r = Math.sqrt(-2 * Math.log(u0));
    let theta = 2 * Math.PI * u1;
    let z0 = r * Math.cos(theta);
    let z1 = r * Math.sin(theta);
    return [z0, z1];
}
let boxMullerNormalRNG_haveSpare = false;
let boxMullerNormalRNG_spare = 0.0;

function boxMullerNormalRNG(): number {
    if (boxMullerNormalRNG_haveSpare) {
        boxMullerNormalRNG_haveSpare = false;
        return boxMullerNormalRNG_spare;
    }
    let u0: number;
    do {
        u0 = Math.random();
    } while (u0 <= 0.0 || u0 >= 1.0);
    
    let u1: number;
    do {
        u1 = Math.random();
    } while (u1 <= 0.0 || u1 >= 1.0);
    let [z0, z1] = boxMullerTransform(u0, u1);
    boxMullerNormalRNG_haveSpare = true;
    boxMullerNormalRNG_spare = z1;
    return z0;
}