boost/variant/variant.hpp
//-----------------------------------------------------------------------------
// boost variant/variant.hpp header file
// See http://www.boost.org for updates, documentation, and revision history.
//-----------------------------------------------------------------------------
//
// Copyright (c) 2002-2003
// 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_VARIANT_HPP
#define BOOST_VARIANT_VARIANT_HPP
#include <cstddef> // for std::size_t
#include <new> // for placement new
#if !defined(BOOST_NO_TYPEID)
#include <typeinfo> // for typeid, std::type_info
#endif // BOOST_NO_TYPEID
#include "boost/variant/detail/config.hpp"
#include "boost/mpl/aux_/config/eti.hpp"
#include "boost/mpl/aux_/value_wknd.hpp"
#include "boost/variant/variant_fwd.hpp"
#include "boost/variant/detail/backup_holder.hpp"
#include "boost/variant/detail/enable_recursive_fwd.hpp"
#include "boost/variant/detail/forced_return.hpp"
#include "boost/variant/detail/initializer.hpp"
#include "boost/variant/detail/make_variant_list.hpp"
#include "boost/variant/detail/over_sequence.hpp"
#include "boost/variant/detail/visitation_impl.hpp"
#include "boost/variant/detail/generic_result_type.hpp"
#include "boost/variant/detail/has_nothrow_move.hpp"
#include "boost/variant/detail/move.hpp"
#include "boost/detail/reference_content.hpp"
#include "boost/aligned_storage.hpp"
#include "boost/blank.hpp"
#include "boost/static_assert.hpp"
#include "boost/preprocessor/cat.hpp"
#include "boost/preprocessor/repeat.hpp"
#include "boost/type_traits/alignment_of.hpp"
#include "boost/type_traits/add_const.hpp"
#include "boost/type_traits/has_nothrow_constructor.hpp"
#include "boost/type_traits/has_nothrow_copy.hpp"
#include "boost/type_traits/is_const.hpp"
#include "boost/type_traits/is_same.hpp"
#include "boost/utility/enable_if.hpp"
#include "boost/variant/recursive_wrapper_fwd.hpp"
#include "boost/variant/static_visitor.hpp"
#include "boost/mpl/eval_if.hpp"
#include "boost/mpl/begin_end.hpp"
#include "boost/mpl/bool.hpp"
#include "boost/mpl/not.hpp"
#include "boost/mpl/empty.hpp"
#include "boost/mpl/find_if.hpp"
#include "boost/mpl/front.hpp"
#include "boost/mpl/identity.hpp"
#include "boost/mpl/if.hpp"
#include "boost/mpl/int.hpp"
#include "boost/mpl/is_sequence.hpp"
#include "boost/mpl/iterator_range.hpp"
#include "boost/mpl/iter_fold_if.hpp"
#include "boost/mpl/logical.hpp"
#include "boost/mpl/max_element.hpp"
#include "boost/mpl/next.hpp"
#include "boost/mpl/deref.hpp"
#include "boost/mpl/pair.hpp"
#include "boost/mpl/protect.hpp"
#include "boost/mpl/push_front.hpp"
#include "boost/mpl/same_as.hpp"
#include "boost/mpl/size_t.hpp"
#include "boost/mpl/sizeof.hpp"
#include "boost/mpl/transform.hpp"
#include "boost/mpl/assert.hpp"
///////////////////////////////////////////////////////////////////////////////
// Implementation Macros:
//
// BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
// Defined in boost/variant/detail/visitation_impl.hpp.
//
// BOOST_VARIANT_MINIMIZE_SIZE
// When #defined, implementation employs all known means to minimize the
// size of variant obje cts. However, often unsuccessful due to alignment
// issues, and potentially harmful to runtime speed, so not enabled by
// default. (TODO: Investigate further.)
#if defined(BOOST_VARIANT_MINIMIZE_SIZE)
# include <climits> // for SCHAR_MAX
# include "boost/mpl/eval_if.hpp"
# include "boost/mpl/equal_to.hpp"
# include "boost/mpl/identity.hpp"
# include "boost/mpl/int.hpp"
# include "boost/mpl/if.hpp"
# include "boost/mpl/less.hpp"
# include "boost/mpl/long.hpp"
# include "boost/mpl/O1_size.hpp"
#endif
namespace boost {
namespace detail { namespace variant {
///////////////////////////////////////////////////////////////////////////////
// (detail) metafunction max_value
//
// Finds the maximum value of the unary metafunction F over Sequence.
//
template <typename Sequence, typename F>
struct max_value
{
private: // helpers, for metafunction result (below)
typedef typename mpl::transform1<Sequence, F>::type transformed_;
typedef typename mpl::max_element<transformed_
>::type max_it;
public: // metafunction result
typedef typename mpl::deref<max_it>::type
type;
};
///////////////////////////////////////////////////////////////////////////////
// (detail) metafunction find_fallback_type
//
// Provides a fallback (i.e., nothrow default-constructible) type from the
// specified sequence, or no_fallback_type if not found.
//
// This implementation is designed to prefer boost::blank over other potential
// fallback types, regardless of its position in the specified sequence.
//
class no_fallback_type;
struct find_fallback_type_pred
{
template <typename Iterator>
struct apply
{
private:
typedef typename mpl::deref<Iterator>::type t_;
public:
typedef mpl::not_< has_nothrow_constructor<t_> > type;
};
};
template <typename Types>
struct find_fallback_type
{
private: // helpers, for metafunction result (below)
typedef typename mpl::end<Types>::type end_it;
// [Find the first suitable fallback type...]
typedef typename mpl::iter_fold_if<
Types
, mpl::int_<0>, mpl::protect< mpl::next<> >
, mpl::protect< find_fallback_type_pred >
>::type first_result_;
typedef typename first_result_::first first_result_index;
typedef typename first_result_::second first_result_it;
// [...now search the rest of the sequence for boost::blank...]
typedef typename mpl::iter_fold_if<
mpl::iterator_range< first_result_it,end_it >
, first_result_index, mpl::protect< mpl::next<> >
, mpl::protect< mpl::not_same_as<boost::blank> >
>::type second_result_;
typedef typename second_result_::second second_result_it;
public: // metafunction result
// [...and return the results of the search:]
typedef typename mpl::eval_if<
is_same< second_result_it,end_it >
, mpl::if_<
is_same< first_result_it,end_it >
, mpl::pair< no_fallback_type,no_fallback_type >
, first_result_
>
, mpl::identity< second_result_ >
>::type type;
};
#if defined(BOOST_MPL_CFG_MSVC_60_ETI_BUG)
template<>
struct find_fallback_type<int>
{
typedef mpl::pair< no_fallback_type,no_fallback_type > type;
};
#endif // BOOST_MPL_CFG_MSVC_60_ETI_BUG workaround
///////////////////////////////////////////////////////////////////////////////
// (detail) metafunction make_storage
//
// Provides an aligned storage type capable of holding any of the types
// specified in the given type-sequence.
//
template <typename Types, typename NeverUsesBackupFlag>
struct make_storage
{
private: // helpers, for metafunction result (below)
typedef typename mpl::eval_if<
NeverUsesBackupFlag
, mpl::identity< Types >
, mpl::push_front<
Types, backup_holder<void*>
>
>::type types;
typedef typename max_value<
types, mpl::sizeof_<mpl::_1>
>::type max_size;
#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551))
typedef typename max_value<
types, alignment_of<mpl::_1>
>::type max_alignment;
#else // borland
// temporary workaround -- use maximal alignment
typedef mpl::size_t< -1 > max_alignment;
#endif // borland workaround
public: // metafunction result
#if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
typedef ::boost::aligned_storage<
BOOST_MPL_AUX_VALUE_WKND(max_size)::value
, BOOST_MPL_AUX_VALUE_WKND(max_alignment)::value
> type;
#else // MSVC7 and below
BOOST_STATIC_CONSTANT(std::size_t, msvc_max_size_c = max_size::value);
BOOST_STATIC_CONSTANT(std::size_t, msvc_max_alignment_c = max_alignment::value);
typedef ::boost::aligned_storage<
msvc_max_size_c
, msvc_max_alignment_c
> type;
#endif // MSVC workaround
};
#if defined(BOOST_MPL_CFG_MSVC_60_ETI_BUG)
template<>
struct make_storage<int,int>
{
typedef int type;
};
#endif // BOOST_MPL_CFG_MSVC_60_ETI_BUG workaround
///////////////////////////////////////////////////////////////////////////////
// (detail) class destroyer
//
// Internal visitor that destroys the value it visits.
//
struct destroyer
: public static_visitor<>
{
public: // visitor interfaces
template <typename T>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(T& operand, int) const
{
operand.~T();
#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551)) || \
BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600))
operand; // suppresses warnings
#endif
BOOST_VARIANT_AUX_RETURN_VOID;
}
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class template known_get
//
// Visitor that returns a reference to content of the specified type.
//
// Precondition: visited variant MUST contain logical content of type T.
//
template <typename T>
class known_get
: public static_visitor<T&>
{
#if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
public: // visitor interface
T& operator()(T& operand) const
{
return operand;
}
template <typename U>
T& operator()(U&) const
{
// logical error to be here: see precondition above
BOOST_ASSERT(false);
return ::boost::detail::variant::forced_return< T& >();
}
#else // MSVC6
private: // helpers, for visitor interface (below)
T& execute(T& operand, mpl::true_) const
{
return operand;
}
template <typename U>
T& execute(U& operand, mpl::false_) const
{
// logical error to be here: see precondition above
BOOST_ASSERT(false);
return ::boost::detail::variant::forced_return< T& >();
}
public: // visitor interface
template <typename U>
T& operator()(U& operand) const
{
typedef typename is_same< U,T >::type
U_is_T;
return execute(operand, U_is_T());
}
#endif // MSVC6 workaround
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class copy_into
//
// Internal visitor that copies the value it visits into the given buffer.
//
class copy_into
: public static_visitor<>
{
private: // representation
void* storage_;
public: // structors
explicit copy_into(void* storage)
: storage_(storage)
{
}
public: // internal visitor interface
template <typename T>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(boost::detail::variant::backup_holder<T>& operand, long) const
{
new(storage_) T( operand.get() );
BOOST_VARIANT_AUX_RETURN_VOID;
}
template <typename T>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(const boost::detail::variant::backup_holder<T>& operand, long) const
{
new(storage_) T( operand.get() );
BOOST_VARIANT_AUX_RETURN_VOID;
}
template <typename T>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(const T& operand, int) const
{
new(storage_) T(operand);
BOOST_VARIANT_AUX_RETURN_VOID;
}
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class assign_storage
//
// Internal visitor that assigns the given storage (which must be a
// constructed value of the same type) to the value it visits.
//
struct assign_storage
: public static_visitor<>
{
private: // representation
const void* rhs_storage_;
public: // structors
explicit assign_storage(const void* rhs_storage)
: rhs_storage_(rhs_storage)
{
}
public: // internal visitor interfaces
template <typename T>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(backup_holder<T>& lhs_content, long) const
{
lhs_content.get()
= static_cast< const backup_holder<T>* >(rhs_storage_)->get();
BOOST_VARIANT_AUX_RETURN_VOID;
}
template <typename T>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(const backup_holder<T>& lhs_content, long) const
{
lhs_content.get()
= static_cast< const backup_holder<T>* >(rhs_storage_)->get();
BOOST_VARIANT_AUX_RETURN_VOID;
}
template <typename T>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(T& lhs_content, int) const
{
// NOTE TO USER :
// Compile error here indicates one of variant's bounded types does
// not meet the requirements of the Assignable concept. Thus,
// variant is not Assignable.
//
// Hint: Are any of the bounded types const-qualified or references?
//
lhs_content = *static_cast< const T* >(rhs_storage_);
BOOST_VARIANT_AUX_RETURN_VOID;
}
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class direct_assigner
//
// Generic static visitor that: if and only if the visited value is of the
// specified type, assigns the given value to the visited value and returns
// true; else returns false.
//
template <typename T>
class direct_assigner
: public static_visitor<bool>
{
private: // representation
const T& rhs_;
public: // structors
explicit direct_assigner(const T& rhs)
: rhs_(rhs)
{
}
#if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
public: // visitor interface
bool operator()(T& lhs)
{
lhs = rhs_;
return true;
}
template <typename U>
bool operator()(U&)
{
return false;
}
#else // MSVC6
private: // helpers, for visitor interface (below)
bool execute(T& lhs, mpl::true_)
{
lhs = rhs_;
return true;
}
template <typename U>
bool execute(U&, mpl::false_)
{
return false;
}
public: // visitor interface
template <typename U>
bool operator()(U& lhs)
{
typedef typename is_same<U,T>::type U_is_T;
return execute(lhs, U_is_T());
}
#endif // MSVC6 workaround
#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600))
private:
// silence MSVC warning C4512: assignment operator could not be generated
direct_assigner& operator= (direct_assigner const&);
#endif
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class backup_assigner
//
// Internal visitor that "assigns" the given value to the visited value,
// using backup to recover if the destroy-copy sequence fails.
//
// NOTE: This needs to be a friend of variant, as it needs access to
// indicate_which, indicate_backup_which, etc.
//
template <typename Variant, typename RhsT>
class backup_assigner
: public static_visitor<>
{
private: // representation
Variant& lhs_;
int rhs_which_;
const RhsT& rhs_content_;
public: // structors
backup_assigner(Variant& lhs, int rhs_which, const RhsT& rhs_content)
: lhs_(lhs)
, rhs_which_(rhs_which)
, rhs_content_(rhs_content)
{
}
private: // helpers, for visitor interface (below)
template <typename LhsT>
void backup_assign_impl(
LhsT& lhs_content
, mpl::true_// has_nothrow_move
)
{
// Move lhs content to backup...
LhsT backup_lhs_content(
::boost::detail::variant::move(lhs_content)
); // nothrow
// ...destroy lhs content...
lhs_content.~LhsT(); // nothrow
try
{
// ...and attempt to copy rhs content into lhs storage:
new(lhs_.storage_.address()) RhsT(rhs_content_);
}
catch (...)
{
// In case of failure, restore backup content to lhs storage...
new(lhs_.storage_.address())
LhsT(
::boost::detail::variant::move(backup_lhs_content)
); // nothrow
// ...and rethrow:
throw;
}
// In case of success, indicate new content type:
lhs_.indicate_which(rhs_which_); // nothrow
}
template <typename LhsT>
void backup_assign_impl(
LhsT& lhs_content
, mpl::false_// has_nothrow_move
)
{
// Backup lhs content...
LhsT* backup_lhs_ptr = new LhsT(lhs_content);
// ...destroy lhs content...
lhs_content.~LhsT(); // nothrow
try
{
// ...and attempt to copy rhs content into lhs storage:
new(lhs_.storage_.address()) RhsT(rhs_content_);
}
catch (...)
{
// In case of failure, copy backup pointer to lhs storage...
new(lhs_.storage_.address())
backup_holder<LhsT>( backup_lhs_ptr ); // nothrow
// ...indicate now using backup...
lhs_.indicate_backup_which( lhs_.which() ); // nothrow
// ...and rethrow:
throw;
}
// In case of success, indicate new content type...
lhs_.indicate_which(rhs_which_); // nothrow
// ...and delete backup:
delete backup_lhs_ptr; // nothrow
}
public: // visitor interface
template <typename LhsT>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(LhsT& lhs_content, int)
{
typedef typename has_nothrow_move_constructor<LhsT>::type
nothrow_move;
backup_assign_impl( lhs_content, nothrow_move() );
BOOST_VARIANT_AUX_RETURN_VOID;
}
#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600))
private:
// silence MSVC warning C4512: assignment operator could not be generated
backup_assigner& operator= (backup_assigner const&);
#endif
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class swap_with
//
// Visitor that swaps visited value with content of given variant.
//
// Precondition: Given variant MUST have same logical type as visited value.
//
template <typename Variant>
struct swap_with
: public static_visitor<>
{
private: // representation
Variant& toswap_;
public: // structors
explicit swap_with(Variant& toswap)
: toswap_(toswap)
{
}
public: // internal visitor interfaces
template <typename T>
void operator()(T& operand) const
{
// Since the precondition ensures types are same, get T...
known_get<T> getter;
T& other = toswap_.apply_visitor(getter);
// ...and swap:
::boost::detail::variant::move_swap( operand, other );
}
private:
swap_with& operator=(const swap_with&);
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class reflect
//
// Generic static visitor that performs a typeid on the value it visits.
//
#if !defined(BOOST_NO_TYPEID)
class reflect
: public static_visitor<const std::type_info&>
{
public: // visitor interfaces
template <typename T>
const std::type_info& operator()(const T&) const
{
return typeid(T);
}
};
#endif // BOOST_NO_TYPEID
///////////////////////////////////////////////////////////////////////////////
// (detail) class comparer
//
// Generic static visitor that compares the content of the given lhs variant
// with the visited rhs content using Comp.
//
// Precondition: lhs.which() == rhs.which()
//
template <typename Variant, typename Comp>
class comparer
: public static_visitor<bool>
{
private: // representation
const Variant& lhs_;
public: // structors
explicit comparer(const Variant& lhs)
: lhs_(lhs)
{
}
public: // visitor interfaces
template <typename T>
bool operator()(const T& rhs_content) const
{
// Since the precondition ensures lhs and rhs types are same, get T...
known_get<const T> getter;
const T& lhs_content = lhs_.apply_visitor(getter);
// ...and compare lhs and rhs contents:
return Comp()(lhs_content, rhs_content);
}
private:
comparer& operator=(const comparer&);
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class equal_comp
//
// Generic function object compares lhs with rhs using operator==.
//
struct equal_comp
{
template <typename T>
bool operator()(const T& lhs, const T& rhs) const
{
return lhs == rhs;
}
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class less_comp
//
// Generic function object compares lhs with rhs using operator<.
//
struct less_comp
{
template <typename T>
bool operator()(const T& lhs, const T& rhs) const
{
return lhs < rhs;
}
};
///////////////////////////////////////////////////////////////////////////////
// (detail) class template invoke_visitor
//
// Internal visitor that invokes the given visitor using:
// * for wrappers (e.g., recursive_wrapper), the wrapper's held value.
// * for all other values, the value itself.
//
template <typename Visitor>
class invoke_visitor
{
private: // representation
Visitor& visitor_;
public: // visitor typedefs
typedef typename Visitor::result_type
result_type;
public: // structors
explicit invoke_visitor(Visitor& visitor)
: visitor_(visitor)
{
}
#if !defined(BOOST_NO_VOID_RETURNS)
public: // internal visitor interfaces
template <typename T>
result_type internal_visit(T& operand, int)
{
return visitor_(operand);
}
# if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0564))
template <typename T>
result_type internal_visit(const T& operand, int)
{
return visitor_(operand);
}
# endif
#else // defined(BOOST_NO_VOID_RETURNS)
private: // helpers, for internal visitor interfaces (below)
template <typename T>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
visit_impl(T& operand, mpl::false_)
{
return visitor_(operand);
}
template <typename T>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
visit_impl(T& operand, mpl::true_)
{
visitor_(operand);
BOOST_VARIANT_AUX_RETURN_VOID;
}
public: // internal visitor interfaces
template <typename T>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
internal_visit(T& operand, int)
{
typedef typename is_same<result_type, void>::type
has_void_result_type;
return visit_impl(operand, has_void_result_type());
}
#endif // BOOST_NO_VOID_RETURNS) workaround
public: // internal visitor interfaces, cont.
template <typename T>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
internal_visit(boost::recursive_wrapper<T>& operand, long)
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
internal_visit(const boost::recursive_wrapper<T>& operand, long)
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
internal_visit(boost::detail::reference_content<T>& operand, long)
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
internal_visit(const boost::detail::reference_content<T>& operand, long)
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
internal_visit(boost::detail::variant::backup_holder<T>& operand, long)
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
internal_visit(const boost::detail::variant::backup_holder<T>& operand, long)
{
return internal_visit( operand.get(), 1L );
}
#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600))
private:
// silence MSVC warning C4512: assignment operator could not be generated
invoke_visitor& operator= (invoke_visitor const&);
#endif
};
}} // namespace detail::variant
///////////////////////////////////////////////////////////////////////////////
// class template variant (concept inspired by Andrei Alexandrescu)
//
// See docs and boost/variant/variant_fwd.hpp for more information.
//
template <
typename T0_
, BOOST_VARIANT_ENUM_SHIFTED_PARAMS(typename T)
>
class variant
{
private: // helpers, for typedefs (below)
typedef variant wknd_self_t;
struct is_recursive_
: detail::variant::is_recursive_flag<T0_>
{
};
typedef typename mpl::eval_if<
is_recursive_
, T0_
, mpl::identity< T0_ >
>::type unwrapped_T0_;
struct is_sequence_based_
: detail::variant::is_over_sequence<unwrapped_T0_>
{
};
#if !defined(BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT)
private: // helpers, for typedefs (below)
typedef typename mpl::eval_if<
is_sequence_based_
, unwrapped_T0_ // over_sequence<...>::type
, detail::variant::make_variant_list<
unwrapped_T0_
, BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T)
>
>::type specified_types;
BOOST_STATIC_ASSERT((
::boost::mpl::not_< mpl::empty<specified_types> >::value
));
typedef typename mpl::eval_if<
is_recursive_
, mpl::transform<
specified_types
, mpl::protect<
detail::variant::quoted_enable_recursive<wknd_self_t>
>
>
, mpl::identity< specified_types >
>::type recursive_enabled_types;
public: // public typedefs
typedef typename mpl::transform<
recursive_enabled_types
, unwrap_recursive<mpl::_1>
>::type types;
private: // internal typedefs
typedef typename mpl::transform<
recursive_enabled_types
, mpl::protect< detail::make_reference_content<> >
>::type internal_types;
typedef typename mpl::front<
internal_types
>::type internal_T0;
#else // defined(BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT)
private: // helpers, for typedefs (below)
typedef unwrapped_T0_ T0;
#define BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS(z,N,_) \
typedef typename mpl::eval_if< \
is_recursive_ \
, detail::variant::enable_recursive< \
BOOST_PP_CAT(T,N) \
, wknd_self_t \
> \
, mpl::identity< BOOST_PP_CAT(T,N) > \
>::type BOOST_PP_CAT(recursive_enabled_T,N); \
/**/
BOOST_PP_REPEAT(
BOOST_VARIANT_LIMIT_TYPES
, BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS
, _
)
#undef BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS
#define BOOST_VARIANT_AUX_UNWRAP_RECURSIVE_TYPEDEFS(z,N,_) \
typedef typename unwrap_recursive< \
BOOST_PP_CAT(recursive_enabled_T,N) \
>::type BOOST_PP_CAT(public_T,N); \
/**/
BOOST_PP_REPEAT(
BOOST_VARIANT_LIMIT_TYPES
, BOOST_VARIANT_AUX_UNWRAP_RECURSIVE_TYPEDEFS
, _
)
#undef BOOST_VARIANT_AUX_UNWRAP_RECURSIVE_TYPEDEFS
public: // public typedefs
typedef typename detail::variant::make_variant_list<
BOOST_VARIANT_ENUM_PARAMS(public_T)
>::type types;
private: // helpers, for internal typedefs (below)
#define BOOST_VARIANT_AUX_MAKE_REFERENCE_CONTENT_TYPEDEFS(z,N,_) \
typedef detail::make_reference_content< \
BOOST_PP_CAT(recursive_enabled_T,N) \
>::type BOOST_PP_CAT(internal_T,N); \
/**/
BOOST_PP_REPEAT(
BOOST_VARIANT_LIMIT_TYPES
, BOOST_VARIANT_AUX_MAKE_REFERENCE_CONTENT_TYPEDEFS
, _
)
#undef BOOST_VARIANT_AUX_MAKE_REFERENCE_CONTENT_TYPEDEFS
private: // internal typedefs
typedef typename detail::variant::make_variant_list<
BOOST_VARIANT_ENUM_PARAMS(internal_T)
>::type internal_types;
private: // static precondition assertions
// NOTE TO USER :
// variant< type-sequence > syntax is not supported on this compiler!
//
BOOST_MPL_ASSERT_NOT(( is_sequence_based_ ));
#endif // BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT workaround
private: // helpers, for representation (below)
typedef typename detail::variant::find_fallback_type<
internal_types
>::type fallback_type_result_;
typedef typename fallback_type_result_::first
fallback_type_index_;
typedef typename fallback_type_result_::second
fallback_type_;
struct has_fallback_type_
: mpl::not_<
is_same< fallback_type_, detail::variant::no_fallback_type >
>
{
};
typedef has_fallback_type_
never_uses_backup_flag;
typedef typename detail::variant::make_storage<
internal_types, never_uses_backup_flag
>::type storage_t;
private: // helpers, for representation (below)
// which_ on:
// * [0, size<internal_types>) indicates stack content
// * [-size<internal_types>, 0) indicates pointer to heap backup
// if which_ >= 0:
// * then which() -> which_
// * else which() -> -(which_ + 1)
#if !defined(BOOST_VARIANT_MINIMIZE_SIZE)
typedef int which_t;
#else // defined(BOOST_VARIANT_MINIMIZE_SIZE)
// [if O1_size available, then attempt which_t size optimization...]
// [select signed char if fewer than SCHAR_MAX types, else signed int:]
typedef typename mpl::eval_if<
mpl::equal_to< mpl::O1_size<internal_types>, mpl::long_<-1> >
, mpl::identity< int >
, mpl::if_<
mpl::less< mpl::O1_size<internal_types>, mpl::int_<SCHAR_MAX> >
, signed char
, int
>
>::type which_t;
#endif // BOOST_VARIANT_MINIMIZE_SIZE switch
// representation -- private when possible
#if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
private:
#else
public:
#endif
which_t which_;
storage_t storage_;
void indicate_which(int which)
{
which_ = static_cast<which_t>( which );
}
void indicate_backup_which(int which)
{
which_ = static_cast<which_t>( -(which + 1) );
}
private: // helpers, for queries (below)
bool using_backup() const
{
return which_ < 0;
}
public: // queries
int which() const
{
// If using heap backup...
if (using_backup())
// ...then return adjusted which_:
return -(which_ + 1);
// Otherwise, return which_ directly:
return which_;
}
private: // helpers, for structors (below)
struct initializer
: BOOST_VARIANT_AUX_INITIALIZER_T(
recursive_enabled_types, recursive_enabled_T
)
{
};
void destroy_content()
{
detail::variant::destroyer visitor;
this->internal_apply_visitor(visitor);
}
public: // structors
~variant()
{
destroy_content();
}
variant()
{
// NOTE TO USER :
// Compile error from here indicates that the first bound
// type is not default-constructible, and so variant cannot
// support its own default-construction.
//
new( storage_.address() ) internal_T0();
indicate_which(0); // zero is the index of the first bounded type
}
private: // helpers, for structors, cont. (below)
class convert_copy_into
: public static_visitor<int>
{
private: // representation
void* storage_;
public: // structors
explicit convert_copy_into(void* storage)
: storage_(storage)
{
}
public: // internal visitor interfaces (below)
template <typename T>
int internal_visit(T& operand, int) const
{
// NOTE TO USER :
// Compile error here indicates one of the source variant's types
// cannot be unambiguously converted to the destination variant's
// types (or that no conversion exists).
//
return initializer::initialize(storage_, operand);
}
# if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0564))
template <typename T>
result_type internal_visit(const T& operand, int) const
{
return initializer::initialize(storage_, operand);
}
# endif
template <typename T>
int internal_visit(boost::detail::reference_content<T>& operand, long) const
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
int internal_visit(const boost::detail::reference_content<T>& operand, long) const
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
int internal_visit(boost::detail::variant::backup_holder<T>& operand, long) const
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
int internal_visit(const boost::detail::variant::backup_holder<T>& operand, long) const
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
int internal_visit(boost::recursive_wrapper<T>& operand, long) const
{
return internal_visit( operand.get(), 1L );
}
template <typename T>
int internal_visit(const boost::recursive_wrapper<T>& operand, long) const
{
return internal_visit( operand.get(), 1L );
}
};
friend class convert_copy_into;
private: // helpers, for structors, below
template <typename T>
void convert_construct(
T& operand
, int
, mpl::false_ = mpl::false_() // is_foreign_variant
)
{
// NOTE TO USER :
// Compile error here indicates that the given type is not
// unambiguously convertible to one of the variant's types
// (or that no conversion exists).
//
indicate_which(
initializer::initialize(
storage_.address()
, operand
)
);
}
template <typename Variant>
void convert_construct(
Variant& operand
, long
, mpl::true_// is_foreign_variant
)
{
convert_copy_into visitor(storage_.address());
indicate_which(
operand.internal_apply_visitor(visitor)
);
}
template <typename Variant>
void convert_construct_variant(Variant& operand)
{
// [Determine if the given variant is itself a bounded type, or if its
// content needs to be converted (i.e., it is a 'foreign' variant):]
//
typedef typename mpl::find_if<
types
, is_same<
add_const<mpl::_1>
, const Variant
>
>::type found_it;
typedef typename mpl::end<types>::type not_found;
typedef typename is_same<
found_it, not_found
>::type is_foreign_variant;
// Convert construct from operand:
convert_construct(
operand, 1L
, is_foreign_variant()
);
}
template <BOOST_VARIANT_ENUM_PARAMS(typename U)>
void convert_construct(
boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>& operand
, long
)
{
convert_construct_variant(operand);
}
template <BOOST_VARIANT_ENUM_PARAMS(typename U)>
void convert_construct(
const boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>& operand
, long
)
{
convert_construct_variant(operand);
}
public: // structors, cont.
#if !defined(BOOST_VARIANT_AUX_BROKEN_CONSTRUCTOR_TEMPLATE_ORDERING)
template <typename T>
variant(const T& operand)
{
convert_construct(operand, 1L);
}
template <typename T>
variant(T& operand)
{
convert_construct(operand, 1L);
}
#elif defined(BOOST_VARIANT_AUX_HAS_CONSTRUCTOR_TEMPLATE_ORDERING_SFINAE_WKND)
// For compilers that cannot distinguish between T& and const T& in
// template constructors, but do fully support SFINAE, we can workaround:
template <typename T>
variant(const T& operand)
{
convert_construct(operand, 1L);
}
template <typename T>
variant(
T& operand
, typename enable_if<
mpl::not_< is_const<T> >
, void
>::type* = 0
)
{
convert_construct(operand, 1L);
}
#else // !defined(BOOST_VARIANT_AUX_HAS_CONSTRUCTOR_TEMPLATE_ORDERING_SFINAE_WKND)
// For compilers that cannot distinguish between T& and const T& in
// template constructors, and do NOT support SFINAE, we can't workaround:
template <typename T>
variant(const T& operand)
{
convert_construct(operand, 1L);
}
#endif // BOOST_VARIANT_AUX_BROKEN_CONSTRUCTOR_TEMPLATE_ORDERING workarounds
public: // structors, cont.
// [MSVC6 requires copy constructor appear after template constructors]
variant(const variant& operand)
{
// Copy the value of operand into *this...
detail::variant::copy_into visitor( storage_.address() );
operand.internal_apply_visitor(visitor);
// ...and activate the *this's primary storage on success:
indicate_which(operand.which());
}
private: // helpers, for modifiers (below)
# if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
template <typename Variant, typename RhsT>
friend class detail::variant::backup_assigner;
# endif
// class assigner
//
// Internal visitor that "assigns" the visited value to the given variant
// by appropriate destruction and copy-construction.
//
class assigner
: public static_visitor<>
{
private: // representation
variant& lhs_;
int rhs_which_;
public: // structors
assigner(variant& lhs, int rhs_which)
: lhs_(lhs)
, rhs_which_(rhs_which)
{
}
private: // helpers, for internal visitor interface (below)
template <typename RhsT, typename B1, typename B2>
void assign_impl(
const RhsT& rhs_content
, mpl::true_// has_nothrow_copy
, B1// has_nothrow_move_constructor
, B2// has_fallback_type
)
{
// Destroy lhs's content...
lhs_.destroy_content(); // nothrow
// ...copy rhs content into lhs's storage...
new(lhs_.storage_.address())
RhsT( rhs_content ); // nothrow
// ...and indicate new content type:
lhs_.indicate_which(rhs_which_); // nothrow
}
template <typename RhsT, typename B>
void assign_impl(
const RhsT& rhs_content
, mpl::false_// has_nothrow_copy
, mpl::true_// has_nothrow_move_constructor
, B// has_fallback_type
)
{
// Attempt to make a temporary copy (so as to move it below)...
RhsT temp(rhs_content);
// ...and upon success destroy lhs's content...
lhs_.destroy_content(); // nothrow
// ...move the temporary copy into lhs's storage...
new(lhs_.storage_.address())
RhsT( detail::variant::move(temp) ); // nothrow
// ...and indicate new content type:
lhs_.indicate_which(rhs_which_); // nothrow
}
template <typename RhsT>
void assign_impl(
const RhsT& rhs_content
, mpl::false_// has_nothrow_copy
, mpl::false_// has_nothrow_move_constructor
, mpl::true_// has_fallback_type
)
{
// Destroy lhs's content...
lhs_.destroy_content(); // nothrow
try
{
// ...and attempt to copy rhs's content into lhs's storage:
new(lhs_.storage_.address())
RhsT( rhs_content );
}
catch (...)
{
// In case of failure, default-construct fallback type in lhs's storage...
new (lhs_.storage_.address())
fallback_type_; // nothrow
// ...indicate construction of fallback type...
lhs_.indicate_which(
BOOST_MPL_AUX_VALUE_WKND(fallback_type_index_)::value
); // nothrow
// ...and rethrow:
throw;
}
// In the event of success, indicate new content type:
lhs_.indicate_which(rhs_which_); // nothrow
}
template <typename RhsT>
void assign_impl(
const RhsT& rhs_content
, mpl::false_// has_nothrow_copy
, mpl::false_// has_nothrow_move_constructor
, mpl::false_// has_fallback_type
)
{
detail::variant::backup_assigner<wknd_self_t, RhsT>
visitor(lhs_, rhs_which_, rhs_content);
lhs_.internal_apply_visitor(visitor);
}
public: // internal visitor interfaces
template <typename RhsT>
BOOST_VARIANT_AUX_RETURN_VOID_TYPE
internal_visit(const RhsT& rhs_content, int)
{
typedef typename has_nothrow_copy<RhsT>::type
nothrow_copy;
typedef typename mpl::or_< // reduces compile-time
nothrow_copy
, detail::variant::has_nothrow_move_constructor<RhsT>
>::type nothrow_move_constructor;
assign_impl(
rhs_content
, nothrow_copy()
, nothrow_move_constructor()
, has_fallback_type_()
);
BOOST_VARIANT_AUX_RETURN_VOID;
}
#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600))
private:
// silence MSVC warning C4512: assignment operator could not be generated
assigner& operator= (assigner const&);
#endif
};
friend class assigner;
void variant_assign(const variant& rhs)
{
// If the contained types are EXACTLY the same...
if (which_ == rhs.which_)
{
// ...then assign rhs's storage to lhs's content:
detail::variant::assign_storage visitor(rhs.storage_.address());
this->internal_apply_visitor(visitor);
}
else
{
// Otherwise, perform general (copy-based) variant assignment:
assigner visitor(*this, rhs.which());
rhs.internal_apply_visitor(visitor);
}
}
private: // helpers, for modifiers (below)
template <typename T>
void assign(const T& rhs)
{
// If direct T-to-T assignment is not possible...
detail::variant::direct_assigner<T> direct_assign(rhs);
if (this->apply_visitor(direct_assign) == false)
{
// ...then convert rhs to variant and assign:
//
// While potentially inefficient, the following construction of a
// variant allows T as any type convertible to one of the bounded
// types without excessive code redundancy.
//
variant temp(rhs);
variant_assign( detail::variant::move(temp) );
}
}
public: // modifiers
template <typename T>
variant& operator=(const T& rhs)
{
assign(rhs);
return *this;
}
// [MSVC6 requires copy assign appear after templated operator=]
variant& operator=(const variant& rhs)
{
variant_assign(rhs);
return *this;
}
void swap(variant& rhs)
{
// If the contained types are the same...
if (which() == rhs.which())
{
// ...then swap the values directly:
detail::variant::swap_with<variant> visitor(rhs);
this->apply_visitor(visitor);
}
else
{
// ...otherwise, perform general variant swap:
variant tmp( detail::variant::move(rhs) );
rhs = detail::variant::move(*this);
*this = detail::variant::move(tmp);
}
}
public: // queries
//
// NOTE: member which() defined above.
//
bool empty() const
{
return false;
}
#if !defined(BOOST_NO_TYPEID)
const std::type_info& type() const
{
detail::variant::reflect visitor;
return this->apply_visitor(visitor);
}
#endif
public: // prevent comparison with foreign types
#if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
# define BOOST_VARIANT_AUX_FAIL_COMPARISON_RETURN_TYPE \
void
#else // MSVC7
//
// MSVC7 gives error about return types for above being different than
// the true comparison operator overloads:
//
# define BOOST_VARIANT_AUX_FAIL_COMPARISON_RETURN_TYPE \
bool
#endif // MSVC7 workaround
template <typename U>
BOOST_VARIANT_AUX_FAIL_COMPARISON_RETURN_TYPE
operator==(const U&) const
{
BOOST_STATIC_ASSERT( false && sizeof(U) );
}
template <typename U>
BOOST_VARIANT_AUX_FAIL_COMPARISON_RETURN_TYPE
operator<(const U&) const
{
BOOST_STATIC_ASSERT( false && sizeof(U) );
}
public: // comparison operators
// [MSVC6 requires these operators appear after template operators]
bool operator==(const variant& rhs) const
{
if (this->which() != rhs.which())
return false;
detail::variant::comparer<
variant, detail::variant::equal_comp
> visitor(*this);
return rhs.apply_visitor(visitor);
}
bool operator<(const variant& rhs) const
{
//
// Dirk Schreib suggested this collating order.
//
if (this->which() != rhs.which())
return this->which() < rhs.which();
detail::variant::comparer<
variant, detail::variant::less_comp
> visitor(*this);
return rhs.apply_visitor(visitor);
}
// helpers, for visitation support (below) -- private when possible
#if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
template < BOOST_VARIANT_ENUM_PARAMS(typename U) >
friend class variant;
private:
#else// defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
public:
#endif// !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
template <typename Visitor, typename VoidPtrCV>
static
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(
typename Visitor::result_type
)
internal_apply_visitor_impl(
int internal_which
, int logical_which
, Visitor& visitor
, VoidPtrCV storage
)
{
typedef mpl::int_<0> first_which;
typedef typename mpl::begin<internal_types>::type first_it;
typedef typename mpl::end<internal_types>::type last_it;
typedef detail::variant::visitation_impl_step<
first_it, last_it
> first_step;
return detail::variant::visitation_impl(
internal_which, logical_which
, visitor, storage, mpl::false_()
, never_uses_backup_flag()
, static_cast<first_which*>(0), static_cast<first_step*>(0)
);
}
template <typename Visitor>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(
typename Visitor::result_type
)
internal_apply_visitor(Visitor& visitor)
{
return internal_apply_visitor_impl(
which_, which(), visitor, storage_.address()
);
}
template <typename Visitor>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(
typename Visitor::result_type
)
internal_apply_visitor(Visitor& visitor) const
{
return internal_apply_visitor_impl(
which_, which(), visitor, storage_.address()
);
}
public: // visitation support
template <typename Visitor>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(
typename Visitor::result_type
)
apply_visitor(Visitor& visitor)
{
detail::variant::invoke_visitor<Visitor> invoker(visitor);
return this->internal_apply_visitor(invoker);
}
template <typename Visitor>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(
typename Visitor::result_type
)
apply_visitor(Visitor& visitor) const
{
detail::variant::invoke_visitor<Visitor> invoker(visitor);
return this->internal_apply_visitor(invoker);
}
}; // class variant
///////////////////////////////////////////////////////////////////////////////
// metafunction make_variant_over
//
// See docs and boost/variant/variant_fwd.hpp for more information.
//
template <typename Types>
struct make_variant_over
{
private: // precondition assertions
#if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
BOOST_STATIC_ASSERT(( ::boost::mpl::is_sequence<Types>::value ));
#endif
public: // metafunction result
typedef variant<
detail::variant::over_sequence< Types >
> type;
};
///////////////////////////////////////////////////////////////////////////////
// function template swap
//
// Swaps two variants of the same type (i.e., identical specification).
//
template < BOOST_VARIANT_ENUM_PARAMS(typename T) >
inline void swap(
variant< BOOST_VARIANT_ENUM_PARAMS(T) >& lhs
, variant< BOOST_VARIANT_ENUM_PARAMS(T) >& rhs
)
{
lhs.swap(rhs);
}
} // namespace boost
// implementation additions
#if !defined(BOOST_NO_IOSTREAM)
#include "boost/variant/detail/variant_io.hpp"
#endif // BOOST_NO_IOSTREAM
#endif // BOOST_VARIANT_VARIANT_HPP