RobustToolbox/Robust.Shared.Maths/RandomExtensions.cs

using System;
using System.Collections.Generic;

namespace Robust.Shared.Maths
{
    public static class RandomExtensions
    {
        /// <summary>
        ///     Generate a random number from a normal (gaussian) distribution.
        /// </summary>
        /// <param name="random">The random object to generate the number from.</param>
        /// <param name="μ">The average or "center" of the normal distribution.</param>
        /// <param name="σ">The standard deviation of the normal distribution.</param>
        public static double NextGaussian(this Random random, double μ = 0, double σ = 1)
        {
            // https://stackoverflow.com/a/218600
            var α = random.NextDouble();
            var β = random.NextDouble();

            var randStdNormal = Math.Sqrt(-2.0 * Math.Log(α)) * Math.Sin(2.0 * Math.PI * β);

            return μ + σ * randStdNormal;
        }

        public static T Pick<T>(this Random random, IReadOnlyList<T> list)
        {
            var index = random.Next(list.Count);
            return list[index];
        }

        public static float NextFloat(this Random random)
        {
            return (float)random.NextDouble();
        }

        /// <summary>
        ///     Have a certain chance to return a boolean.
        /// </summary>
        /// <param name="random">The random instance to run on.</param>
        /// <param name="chance">The chance to pass, from 0 to 1.</param>
        public static bool Prob(this Random random, float chance)
        {
            return random.NextDouble() <= chance;
        }
    }
}