C++11 enum attribute set template

/*
 * Copyright 2013 Florian Philipp
 *
 * 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.
 */
#include <bitset>
#include <cassert>

namespace {

  template<class EnumClass, EnumClass min, EnumClass max>
  class EnumSet
  {
    /* static_cast to size_t works in all cases, even when underlying enum
     * values are negative
     */
    typedef std::bitset<
      static_cast<std::size_t>(max) - static_cast<std::size_t>(min) + 1> set_t;
    set_t set;
  public:
    typedef typename set_t::reference reference;
    reference operator[](EnumClass e)
    {
      return set[static_cast<std::size_t>(e) - static_cast<std::size_t>(min)];
    }
    bool operator[](EnumClass e) const
    {
      return set[static_cast<std::size_t>(e) - static_cast<std::size_t>(min)];
    }
  };
  enum class Source {
    analog_radio, internet_radio, bluetooth
  };
  typedef EnumSet<Source, Source::analog_radio, Source::bluetooth> SourceSet;
}

int main()
{
  SourceSet attributes;
  attributes[Source::analog_radio] = true;
  attributes[Source::bluetooth] = true;
  assert(attributes[Source::analog_radio] == true);
  assert(attributes[Source::internet_radio] == false);
  assert(attributes[Source::bluetooth] == true);
  return 0;
}