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/// \file utils/optional.hpp

/// Provides the utils::optional class.

///

/// The class is provided as a separate module on its own to minimize

/// header-inclusion side-effects.

#if !defined(UTILS_OPTIONAL_HPP)

#define UTILS_OPTIONAL_HPP

#include "utils/optional_fwd.hpp"

#include <ostream>

namespace utils {

/// Holds a data value or none.

///

/// This class allows users to represent values that may be uninitialized.

/// Instead of having to keep separate variables to track whether a variable is

/// supposed to have a value or not, this class allows multiplexing the

/// behaviors.

///

/// This class is a simplified version of Boost.Optional.

template< class T >

class optional {

    /// Internal representation of the optional data value.

    T* _data;

public:

    optional(void);

    optional(utils::detail::none_t);

    optional(const optional< T >&);

    explicit optional(const T&);

    ~optional(void);

    optional& operator=(utils::detail::none_t);

    optional& operator=(const T&);

    optional& operator=(const optional< T >&);

    bool operator==(const optional< T >&) const;

    bool operator!=(const optional< T >&) const;

    operator bool(void) const;

    const T& get(void) const;

    const T& get_default(const T&) const;

    T& get(void);

};

template< class T >

std::ostream& operator<<(std::ostream&, const optional< T >&);

template< class T >

optional< T > make_optional(const T&);

}  // namespace utils

#endif  // !defined(UTILS_OPTIONAL_HPP)