hierarchygenerators.h

exmat - The Expression Template Matrix Library,是矩阵运算模板库

////////////////////////////////////////////////////////////////////////////////
// helper class template FieldHelper
// See Field below
////////////////////////////////////////////////////////////////////////////////
    
    template <unsigned int i>
    struct FieldHelper
    {            
        template<class H, class Unit>
        struct In
        {
        private:
            typedef typename TL::TypeAt<typename H::TList, i>::Result ElementType;
            typedef typename ApplyInnerType<Unit, ElementType>::type UnitType;
            
            enum { isConst = TypeTraits<H>::isConst };
			
            typedef typename Select
            <
                isConst,
                const typename H::RightBase,
                typename H::RightBase
            > 
            ::Result RightBase;
			
			
            typedef typename Select
            <
                IsEqualType<UnitType, TupleUnit<ElementType> >::value, 
                ElementType, 
                UnitType
            >
            ::Result UnqualifiedResultType;
			
        public:
            typedef typename Select
            <
                isConst,
                const UnqualifiedResultType,
                UnqualifiedResultType
            >
            ::Result ResultType;
            
            // Must be a template, don't know why.
			// If Do is not a template and H& is used as parameter
			// MSVC will give a linker error.
			template <class T>
			static ResultType& Do(H& obj, T*)
            {
                //typedef typename T::RightBase RightBase;
				//RightBase& rightBase = obj;
				RightBase& rightBase = obj;
                return FieldHelper<i - 1>::template In<RightBase, Unit>::Do(rightBase, (int*)0);
            }
        };
    };

    template <>
    struct FieldHelper<0>
    {            
        template<class H, class Unit>
        struct In
        {
        private:
            typedef typename H::TList::Head ElementType;
            typedef typename ApplyInnerType<Unit, ElementType>::type UnitType;
            
            enum { isConst = TypeTraits<H>::isConst };

            typedef typename Select
            <
                isConst,
                const typename H::LeftBase,
                typename H::LeftBase
            > 
            ::Result LeftBase;

            typedef typename Select
            <
                IsEqualType<UnitType, TupleUnit<ElementType> >::value, 
                ElementType, 
                UnitType
            >
            ::Result UnqualifiedResultType;
			
        public:
            typedef typename Select
            <
                isConst,
                const UnqualifiedResultType,
                UnqualifiedResultType
            >
            ::Result ResultType;
            
		public:
            template <class T>
			static ResultType& Do(H& obj, T*)
            {
                LeftBase& leftBase = obj;
                return leftBase;
            }
        };
    };

////////////////////////////////////////////////////////////////////////////////
// function template Field
// Accesses a field in an object of a type generated with GenScatterHierarchy
// Invocation (obj is an object of a type H generated with GenScatterHierarchy,
//     i is the index of a type in the typelist used to generate H):
// Field<i>(obj)
// returns a reference to Unit<T>, where Unit is the template used to generate H
//     and T is the i-th type in the typelist 
////////////////////////////////////////////////////////////////////////////////
	/*
	template <unsigned int i, class TList, class UnitWrapper>
    typename FieldHelper<i>::template In<GenScatterHierarchy<TList, UnitWrapper>,UnitWrapper>::ResultType&
    Field(GenScatterHierarchy<TList, UnitWrapper>& obj, Int2Type<i>)
    {
		typedef typename GenScatterHierarchy<TList, UnitWrapper> H;
		return FieldHelper<i>::template In<H, UnitWrapper>::Do(obj, (int*)0);
    }
	*/
	template <unsigned int i, class TList, class UnitWrapper>
    typename FieldHelper<i>::template In<GenScatterHierarchy<TList, UnitWrapper>,UnitWrapper>::ResultType&
    Field(GenScatterHierarchy<TList, UnitWrapper>& obj, Int2Type<i>* = (Int2Type<i>*)0)
    {
		typedef typename GenScatterHierarchy<TList, UnitWrapper> H;
		return FieldHelper<i>::template In<H, UnitWrapper>::Do(obj, (int*)0);
    }
////////////////////////////////////////////////////////////////////////////////
// class template GenLinearHierarchy
// Generates a linear hierarchy starting from a typelist and a template
// Invocation (TList is a typelist, Model is a template of two args):
// GenScatterHierarchy<TList, Model>
////////////////////////////////////////////////////////////////////////////////
//	VC 6.0 changes:
//	see GenScatterHierarchy 

	template
    <
        class TList,
        class Unit,
        class Root = EmptyType
    >
    class GenLinearHierarchy;

namespace Private
{
    
    template <typename TListTag> 
    struct GenLinearHierarchyHelper
    {
        template<class TList, class Unit, class Root>
        struct In 
        {
            typedef typename TList::ERROR_THIS_INSTANCE_SELECTED Result; 
        };
    };
    
    template <> 
	struct GenLinearHierarchyHelper<TL::Private::Typelist_tag>
    {
        template<class TList, class Unit, class Root>
        struct In 
        {
        private:
            typedef typename TList::Head Head;
            typedef typename TList::Tail Tail;

        public:
            typedef typename
			ApplyInnerType2<Unit, Head, GenLinearHierarchy<Tail, Unit, Root> >::type Result; 
        };
    };

    template <> 
	struct GenLinearHierarchyHelper<TL::Private::NullType_tag>
    {
        template<class TList, class Unit, class Root>
        struct In
        {
        private:
            typedef typename TList::Head Head;

        public:
            typedef typename ApplyInnerType2<Unit,Head, Root>::type Result;
        };
    };
	
	template <class T, class U, class Root>
	struct Wrap
	{
		struct Dummy {};
		typedef typename T::Tail Tail;
		
		// create the hierarchy 
		typedef typename Private::GenLinearHierarchyHelper
          <
			typename TL::Private::IsTypelist<Tail>::type_tag
          >
          ::template In<T, U, Root>::Result TempType;
		
		typedef Private::VC_Base_Workaround<TempType, Dummy> type;
		
		// this is nothing more than a typedef to the created hierarchy (TempType).
		// But if we try to inherit directly from TempType VC 6.0
		// will produce a "Error C2516. : is not a legal base class."
		typedef typename type::LeftBase Base;
	};
} // namespace Private

	// Trying to inherit from LinBase will result in "Error C2516. : is not a legal base class."
	// Private::Wrap introduces some levels of indirections which will
	// make the vc happy.
	template
    <
        class TList,
        class Unit,
        class Root
    >
    class GenLinearHierarchy : public Private::Wrap<TList, Unit, Root>::Base
    {
        ASSERT_TYPELIST(TList); // TList must not be NullType

    public:
        typedef typename Private::GenLinearHierarchyHelper
        <
			typename TL::Private::IsTypelist<typename TList::Tail>::type_tag
        >
        ::template In<TList, Unit, Root>::Result LinBase;
    };

}   // namespace Loki

#if defined (_MSC_VER) && _MSC_VER <= 1300
#define FIELD(Obj, Nr) \
	Field(Obj, (Int2Type<Nr>*)0)
#else
#define FIELD(Obj, Nr) \
	Field<Nr>(Obj)
#endif

////////////////////////////////////////////////////////////////////////////////
// Change log:
// June 20, 2001: ported by Nick Thurn to gcc 2.95.3. Kudos, Nick!!!
// September 16, 2002: Fixed dependent template, using "::template" syntax. T.S.
// Oct  24, 2002: ported by Benjamin Kaufmann to MSVC 6 
// Dec	08, 2002: Fixed problems with MSVC6-Version of GenScatterHierarchy when
//					used with typelists containing equal types. B.K.
//					New Version is ugly :-(
// Dec	08, 2002: Interface changed for Field-Function. The old version does not
//					work correctly due to the "Explicitly Specified Template 
//					Functions Not Overloaded Correctly"-Bug 
//					(Microsoft KB Article - 240871). B.K.
// Mar	08, 2003: New transparent workaround for Field-Functions. The FIELD-Macro
//					is no longer needed. B.K.
////////////////////////////////////////////////////////////////////////////////
#undef IS_TYPELIST
#endif // HIERARCHYGENERATORS_INC_