//-----------------------------------------------------------------------------

// boost variant/get.hpp header file

// See http://www.boost.org for updates, documentation, and revision history.

//-----------------------------------------------------------------------------

//

// Copyright (c) 2003

// Eric Friedman, Itay Maman

//

// Distributed under the Boost Software License, Version 1.0. (See

// accompanying file LICENSE_1_0.txt or copy at

// http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_VARIANT_GET_HPP

#define BOOST_VARIANT_GET_HPP

#include <exception>

#include "boost/config.hpp"

#include "boost/detail/workaround.hpp"

#include "boost/utility/addressof.hpp"

#include "boost/variant/variant_fwd.hpp"

#include "boost/type_traits/add_reference.hpp"

#include "boost/type_traits/add_pointer.hpp"

#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

#   include "boost/mpl/bool.hpp"

#   include "boost/mpl/or.hpp"

#   include "boost/type_traits/is_same.hpp"

#endif

namespace boost {

//////////////////////////////////////////////////////////////////////////

// class bad_get

//

// The exception thrown in the event of a failed get of a value.

//

class bad_get

    : public std::exception

{

public: // std::exception implementation

    virtual const char * what() const throw()

    {

        return "boost::bad_get: "

               "failed value get using boost::get";

    }

};

//////////////////////////////////////////////////////////////////////////

// function template get<T>

//

// Retrieves content of given variant object if content is of type T.

// Otherwise: pointer ver. returns 0; reference ver. throws bad_get.

//

namespace detail { namespace variant {

// (detail) class template get_visitor

//

// Generic static visitor that: if the value is of the specified type,

// returns a pointer to the value it visits; else a null pointer.

//

template <typename T>

struct get_visitor

{

private: // private typedefs

    typedef typename add_pointer<T>::type pointer;

    typedef typename add_reference<T>::type reference;

public: // visitor typedefs

    typedef pointer result_type;

public: // visitor interfaces

#if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)

    pointer operator()(reference operand) const

    {

        return boost::addressof(operand);

    }

    template <typename U>

    pointer operator()(const U&) const

    {

        return static_cast<pointer>(0);

    }

#else // MSVC6

private: // helpers, for visitor interfaces (below)

    pointer execute_impl(reference operand, mpl::true_) const

    {

        return boost::addressof(operand);

    }

    template <typename U>

    pointer execute_impl(const U& operand, mpl::false_) const

    {

        return static_cast<pointer>(0);

    }

public: // visitor interfaces

    template <typename U>

    pointer operator()(U& operand) const

    {

        // MSVC6 finds normal implementation (above) ambiguous,

        // so we must explicitly disambiguate

        typedef typename mpl::or_<

              is_same<U, T>

            , is_same<const U, T>

            >::type U_is_T;

        return execute_impl(operand, U_is_T());

    }

#endif // MSVC6 workaround

};

}} // namespace detail::variant

#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551))

#   define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \

    BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(t)

#else

#   define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \

    , t* = 0

#endif

template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >

inline

    typename add_pointer<U>::type

get(

      boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand

      BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)

    )

{

    typedef typename add_pointer<U>::type U_ptr;

    if (!operand) return static_cast<U_ptr>(0);

    detail::variant::get_visitor<U> v;

    return operand->apply_visitor(v);

}

template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >

inline

    typename add_pointer<const U>::type

get(

      const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand

      BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)

    )

{

    typedef typename add_pointer<const U>::type U_ptr;

    if (!operand) return static_cast<U_ptr>(0);

    detail::variant::get_visitor<const U> v;

    return operand->apply_visitor(v);

}

template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >

inline

    typename add_reference<U>::type

get(

      boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand

      BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)

    )

{

    typedef typename add_pointer<U>::type U_ptr;

    U_ptr result = get<U>(&operand);

    if (!result)

        throw bad_get();

    return *result;

}

template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >

inline

    typename add_reference<const U>::type

get(

      const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand

      BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)

    )

{

    typedef typename add_pointer<const U>::type U_ptr;

    U_ptr result = get<const U>(&operand);

    if (!result)

        throw bad_get();

    return *result;

}

} // namespace boost

#endif // BOOST_VARIANT_GET_HPP