source: branches/PushGP/HeuristicLab.PushGP/HeuristicLab.Problems.ProgramSynthesis/Push/Generators/NameGenerator.cs @ 14727

namespace HeuristicLab.Problems.ProgramSynthesis.Push.Generators {
  using System;
  using HeuristicLab.Core;
  using HeuristicLab.Random;

  public class NameGenerator {
    public const int DefaultRandomNameLength = 10;

    private static readonly char[] chars =
      "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".ToCharArray();

    private int index;

    public string GetNext() {
      var length = this.index < chars.Length ? 1 : (int)Math.Log(this.index, chars.Length) + 1;
      var result = new char[length];
      var tmp = this.index;
      this.index++;

      for (var i = length; i > 0; i--) {
        var a = (int)Math.Pow(chars.Length, i - 1);
        var b = tmp / a;

        result[length - i] = chars[b];

        tmp -= a * b;
      }

      return new string(result);
    }

    public static string RandomName(IRandom random) {
      return RandomName(DefaultRandomNameLength, random);
    }

    public static string RandomName(int length = DefaultRandomNameLength, IRandom random = null) {
      random = random ?? new FastRandom();
      var name = new char[length];

      for (var i = 0; i < length; i++)
        name[i] = chars[random.Next(chars.Length)];

      return new string(name);
    }
  }
}