/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  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
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  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.
 *
 *=========================================================================*/
#ifndef itkBoolean_h
#define itkBoolean_h

namespace itk
{

/**
 * \class Boolean
 *
 * \brief An alternative to bool for additional thread safety
 *
 * The class `Boolean` provides an alternative to `bool`. `std::vector<bool>` is not thread safe due to the possibility
 * of multiple bits being packed together in the same memory location.  std::vector<Boolean> does not have such a space
 * optimization. std::vector<Boolean> is semantically like `std::vector<bool>`, but unlike `std::vector<bool>`, it does
 * "avoid data races when the contents of the contained object in different elements in the same container [...] are
 * modified concurrently", according to the C++ Standard, section [container.requirements.dataraces], "Container data
 * races".
 *
 * \ingroup ITKCommon
 */
class Boolean
{
public:
  /** Supports default construction */
  constexpr Boolean() = default;

  /** Supports implicit conversion from `bool`. */
  constexpr Boolean(bool v)
    : m_Value(v)
  {}

  /** Supports implicit conversion to `bool`. */
  constexpr operator bool() const { return m_Value; }

private:
  bool m_Value = false;
};

} // namespace itk

#endif