source: branches/2895_PushGP_GenealogyAnalysis/HeuristicLab.Problems.ProgramSynthesis/Push/Extensions/EnumExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace HeuristicLab.Problems.ProgramSynthesis {
  public static class EnumExtensions {
    public static T ToMask<T>(this IEnumerable<T> values) where T : struct, IConvertible {
      if (!typeof(T).IsEnum)
        throw new ArgumentException("T must be an enumerated type.");

      var builtValue = Enum
        .GetValues(typeof(T))
        .Cast<T>()
        .Where(values.Contains)
        .Aggregate(0, (current, value) => current | Convert.ToInt32(value));

      return (T)Enum.Parse(typeof(T), builtValue.ToString());
    }

    public static IEnumerable<T> ToValues<T>(this T flags) where T : struct, IConvertible {
      if (!typeof(T).IsEnum)
        throw new ArgumentException("T must be an enumerated type.");

      var inputInt = (int)(object)flags;
      foreach (T value in Enum.GetValues(typeof(T))) {
        var valueInt = (int)(object)value;
        if (0 != (valueInt & inputInt)) {
          yield return value;
        }
      }
    }
  }
}