typelist.h

loki库的源代码。loki库是以模板技术和面向对象技术为基础的c++类库。

{
	template <class TList>
	struct EraseImpl
	{	// TList is not NullType.
		// Check if TList::Head is equal to T
		// if T is the same as TList::Head, then the Result is TList::Tail
		//
		// if TList is not NullType and TList::Head is not equal to T,
		// then the Result is a Typelist having TList::Head as its Head
		// and the result of applying Erase to the tail of list as its
		// tail.
		template <class T>
		struct In
		{
			ASSERT_TYPELIST(TList);
			typedef typename TList::Head Head;
			typedef typename TList::Tail Tail;
			typedef typename Select
			<
				IsEqualType<Head, T>::value,	// is T equal to Head?
				Tail,							// Yes. Result is tail
				Typelist<typename TList::Head,	// No. recurse
				typename Erase<typename TList::Tail, T>::Result>
			>::Result Result;

		};
	};

	// if TList is NullType the result is NullType.
	template <>
	struct EraseImpl<NullType>
	{
		template <class T>
		struct In
		{
			typedef NullType Result;
		};
	};
}	// end of namespace Private

	template <class TList, class T>
	struct Erase
	{
		typedef typename Private::EraseImpl<TList>::template In<T>::Result Result;
	};

////////////////////////////////////////////////////////////////////////////////
// class template EraseAll
// Erases all occurences, if any, of a type in a typelist
// Invocation (TList is a typelist and T is a type):
// EraseAll<TList, T>::Result
// returns a typelist that is TList without any occurence of T
////////////////////////////////////////////////////////////////////////////////
	template <class TList, class T>
	struct EraseAll;
namespace Private
{
	template <class TList>
	struct EraseAllImpl
	{	// TList is not NullType.
		// Check if TList::Head is equal to T
		// If T is equal to TLIst::Head the result is the result of EraseAll
		// applied to TList::Tail
		//
		// If T is not equal to TList::Head the result is a Typelist with
		// TList::Head as its head and the result of applying EraseAll to TList::Tail
		// as its tail.
		template <class T>
		struct In
		{
			ASSERT_TYPELIST(TList);
			typedef typename TList::Head Head;
			typedef typename TList::Tail Tail;
			typedef typename Select
			<
				IsEqualType<Head, T>::value,				// is T == Head?
				typename EraseAll<Tail, T>::Result,			// Yes
				Typelist<Head, typename						// No
				EraseAll<Tail, T>::Result>
			>::Result Result;
		};
	};

	// if TList is NullType the result is NullType.
	template <>
	struct EraseAllImpl<NullType>
	{
		template <class T>
		struct In
		{
			typedef NullType Result;
		};
	};
}	// end of namespace Private

	template <class TList, class T>
	struct EraseAll
	{
		typedef typename Private::EraseAllImpl<TList>::template In<T>::Result Result;
	};

////////////////////////////////////////////////////////////////////////////////
// class template NoDuplicates
// Removes all duplicate types in a typelist
// Invocation (TList is a typelist):
// NoDuplicates<TList, T>::Result
////////////////////////////////////////////////////////////////////////////////
// NoDuplicates taken from Rani Sharoni's Loki VC7-Port.
	template <class TList>
    struct NoDuplicates
    {
    private:
        typedef typename TList::Head Head;
        typedef typename TList::Tail Tail;

        ASSERT_TYPELIST(TList);

        typedef typename NoDuplicates<Tail>::Result L1;
        typedef typename Erase<L1, Head>::Result    L2;

    public:
        typedef Typelist<Head, L2> Result;
    };

    template <>
    struct NoDuplicates<NullType>
    {
        typedef NullType Result;
    };
////////////////////////////////////////////////////////////////////////////////
// class template Replace
// Replaces the first occurence of a type in a typelist, with another type
// Invocation (TList is a typelist, T, U are types):
// Replace<TList, T, U>::Result
// returns a typelist in which the first occurence of T is replaced with U
////////////////////////////////////////////////////////////////////////////////
	template <class TList, class T, class U>
	struct Replace;
namespace Private
{
	// If TList is not NullType, check if T is equal to TList::Head
	template <class TList>
	struct ReplaceImpl
	{
		template <class T, class U>
		struct In
		{
			// If TList::Head is equal to T, the result is a typelist
			// with U as its head an TList::Tail as its tail.
			// If T is not equal to TList::Head, the result is a typelist
			// with TList::Head as its head and the result of applying
			// Replace to TList::Tail, T, U as its tail
			ASSERT_TYPELIST(TList);
			typedef typename TList::Head Head;
			typedef typename TList::Tail Tail;
			typedef typename Select
			<
				IsEqualType<T, Head>::value,	// Is T == Head?
				Typelist<U, Tail>,				// yes
				Typelist<Head, typename Replace<Tail, T, U>::Result>
			>::Result Result;
		};
	};

	// If TList is NullType the result is NullType
	template <>
	struct ReplaceImpl<NullType>
	{
		template <class T, class U>
		struct In
		{
			typedef NullType Result;
		};
	};
}	// end of namespace Private

	template <class TList, class T, class U>
	struct Replace
	{
		typedef typename
		Private::ReplaceImpl<TList>::template In<T, U>::Result Result;
	};

////////////////////////////////////////////////////////////////////////////////
// class template ReplaceAll
// Replaces all occurences of a type in a typelist, with another type
// Invocation (TList is a typelist, T, U are types):
// Replace<TList, T, U>::Result
// returns a typelist in which all occurences of T is replaced with U
////////////////////////////////////////////////////////////////////////////////
	template <class TList, class T, class U>
	struct ReplaceAll;

namespace Private
{
	// If TList is not NullType, check if T is equal to TList::Head
	template <class TList>
	struct ReplaceAllImpl
	{
		template <class T, class U>
		struct In
		{
			ASSERT_TYPELIST(TList);
			typedef typename TList::Head Head;
			typedef typename TList::Tail Tail;
			typedef typename Select
			<
				IsEqualType<T, Head>::value,							// Is T == Head?
				Typelist<U, typename ReplaceAll<Tail, T, U>::Result>,	// yes
				Typelist<Head, typename ReplaceAll<Tail, T, U>::Result>
			>::Result Result;
		};
	};

	// If TList is NullType the result is NullType
	template <>
	struct ReplaceAllImpl<NullType>
	{
		template <class T, class U>
		struct In
		{
			typedef NullType Result;
		};
	};
}
	template <class TList, class T, class U>
	struct ReplaceAll
	{
		typedef typename
		Private::ReplaceAllImpl<TList>::template In<T, U>::Result Result;
	};

////////////////////////////////////////////////////////////////////////////////
// class template Reverse
// Reverses a typelist
// Invocation (TList is a typelist):
// Reverse<TList>::Result
// returns a typelist that is TList reversed
////////////////////////////////////////////////////////////////////////////////
//	Reverse taken from Rani Sharoni's Loki VC7-Port.
	template <class TList> struct Reverse;

    template <>
    struct Reverse<NullType>
    {
        typedef NullType Result;
    };

    template <class TList>
    struct Reverse
    {
    private:
        typedef typename TList::Head Head;
        typedef typename TList::Tail Tail;

        ASSERT_TYPELIST(TList);

    public:
        typedef typename Append<
            typename Reverse<Tail>::Result, Head>::Result Result;
    };

////////////////////////////////////////////////////////////////////////////////
// class template MostDerived
// Finds the type in a typelist that is the most derived from a given type
// Invocation (TList is a typelist, T is a type):
// MostDerived<TList, T>::Result
// returns the type in TList that's the most derived from T
////////////////////////////////////////////////////////////////////////////////
	template <class TList, class T> struct MostDerived;
namespace Private
{
	template <class TList>
	struct MostDerivedImpl
	{
		template <class T>
		struct In
		{
			private:
				ASSERT_TYPELIST(TList);
				typedef typename TList::Head Head;
				typedef typename TList::Tail Tail;
				typedef typename MostDerived<Tail, T>::Result Candidate;
			public:
				typedef typename Select
				<
					SUPERSUBCLASS(Candidate, Head),
					Head,
					Candidate
				>::Result Result;
		};
	};
	template <>
	struct MostDerivedImpl<NullType>
	{
		template <class T>
		struct In {typedef T Result;};
	};
}	// end of namespace Private

	template <class TList, class T>
	struct MostDerived
	{
		typedef typename
		Private::MostDerivedImpl<TList>::template In<T>::Result Result;
	};
////////////////////////////////////////////////////////////////////////////////
// class template DerivedToFront
// Arranges the types in a typelist so that the most derived types appear first
// Invocation (TList is a typelist):
// DerivedToFront<TList>::Result
// returns the reordered TList
////////////////////////////////////////////////////////////////////////////////
	template <class TList>
    struct DerivedToFront
    {
    private:
        ASSERT_TYPELIST(TList);

        typedef typename TList::Head Head;
        typedef typename TList::Tail Tail;

        typedef typename MostDerived<Tail, Head>::Result TheMostDerived;
        typedef typename Replace<Tail, TheMostDerived, Head>::Result Temp;
        typedef typename DerivedToFront<Temp>::Result L;

    public:
        typedef Typelist<TheMostDerived, L> Result;
    };

	template <>
	struct DerivedToFront<NullType>
	{
		typedef NullType Result;
	};

////////////////////////////////////////////////////////////////////////////////
// class template DerivedToFrontAll
// Arranges all the types in a typelist so that the most derived types appear first
// Invocation (TList is a typelist):
// DerivedToFront<TList>::Result
// returns the reordered TList
////////////////////////////////////////////////////////////////////////////////
// DerivedToFrontAll taken from Rani Sharoni's Loki VC7-Port.
	template <class TList>
    struct DerivedToFrontAll
    {
		private:
			ASSERT_TYPELIST(TList);

			typedef typename TList::Head Head;
			typedef typename TList::Tail Tail;

			typedef typename MostDerived<Tail, Head>::Result TheMostDerived;
			typedef typename Replace<Tail, TheMostDerived, Head>::Result L;

			typedef typename DerivedToFrontAll<L>::Result TailResult;

		public:
			typedef Typelist<TheMostDerived, TailResult> Result;
    };

    template <>
    struct DerivedToFrontAll<NullType>
    {
        typedef NullType Result;
    };


	}	// end of namespace TL
}	// end of namespace Loki
////////////////////////////////////////////////////////////////////////////////
// Change log:
// June 09, 2001: Fix bug in parameter list of macros TYPELIST_23 to TYPELIST_27
//      (credit due to Dave Taylor)
// June 20, 2001: ported by Nick Thurn to gcc 2.95.3. Kudos, Nick!!!
// May  10, 2002: ported by Rani Sharoni to VC7 (RTM - 9466)
// Sept 29, 2002: ported by Benjamin Kaufmann to MSVC 6.0
// Feb	24, 2003: renamed MakeTypeList to MakeTypelist. Fixed a bug in
//					DerivedToFront.
////////////////////////////////////////////////////////////////////////////////
#endif // TYPELIST_INC_