269 lines
8.9 KiB
C
269 lines
8.9 KiB
C
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////////////////////////////////////////////////////////////////////////////////
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// The Loki Library
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// Copyright (c) 2001 by Andrei Alexandrescu
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// This code accompanies the book:
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// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design
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// Patterns Applied". Copyright (c) 2001. Addison-Wesley.
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// Permission to use, copy, modify, distribute and sell this software for any
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// purpose is hereby granted without fee, provided that the above copyright
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// notice appear in all copies and that both that copyright notice and this
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// permission notice appear in supporting documentation.
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// The author or Addison-Wesley Longman make no representations about the
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// suitability of this software for any purpose. It is provided "as is"
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// without express or implied warranty.
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////////////////////////////////////////////////////////////////////////////////
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// Last update: August 9, 2002
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#ifndef HIERARCHYGENERATORS_INC_
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#define HIERARCHYGENERATORS_INC_
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#include "Typelist.h"
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#include "TypeTraits.h"
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#include "EmptyType.h"
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namespace Loki
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{
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////////////////////////////////////////////////////////////////////////////////
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// class template GenScatterHierarchy
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// Generates a scattered hierarchy starting from a typelist and a template
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// Invocation (TList is a typelist, Model is a template of one arg):
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// GenScatterHierarchy<TList, Model>
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// The generated class inherits all classes generated by instantiating the
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// template 'Model' with the types contained in TList
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////////////////////////////////////////////////////////////////////////////////
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template <class TList, template <class> class Unit>
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class GenScatterHierarchy;
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template <class T1, class T2, template <class> class Unit>
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class GenScatterHierarchy<Typelist<T1, T2>, Unit>
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: public GenScatterHierarchy<T1, Unit>
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, public GenScatterHierarchy<T2, Unit>
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{
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public:
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typedef Typelist<T1, T2> TList;
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typedef GenScatterHierarchy<T1, Unit> LeftBase;
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typedef GenScatterHierarchy<T2, Unit> RightBase;
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template <typename T> struct Rebind
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{
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typedef Unit<T> Result;
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};
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};
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template <class AtomicType, template <class> class Unit>
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class GenScatterHierarchy : public Unit<AtomicType>
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{
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typedef Unit<AtomicType> LeftBase;
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template <typename T> struct Rebind
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{
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typedef Unit<T> Result;
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};
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};
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template <template <class> class Unit>
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class GenScatterHierarchy<NullType, Unit>
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{
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template <typename T> struct Rebind
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{
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typedef Unit<T> Result;
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};
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};
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////////////////////////////////////////////////////////////////////////////////
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// function template Field
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// Accesses a field in an object of a type generated with GenScatterHierarchy
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// Invocation (obj is an object of a type H generated with GenScatterHierarchy,
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// T is a type in the typelist used to generate H):
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// Field<T>(obj)
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// returns a reference to Unit<T>, where Unit is the template used to generate H
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////////////////////////////////////////////////////////////////////////////////
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template <class T, class H>
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typename H::template Rebind<T>::Result& Field(H& obj)
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{
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return obj;
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}
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template <class T, class H>
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const typename H::template Rebind<T>::Result& Field(const H& obj)
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{
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return obj;
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}
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////////////////////////////////////////////////////////////////////////////////
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// function template TupleUnit
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// The building block of tuples
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////////////////////////////////////////////////////////////////////////////////
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template <class T>
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struct TupleUnit
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{
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T value_;
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operator T&() { return value_; }
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operator const T&() const { return value_; }
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};
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////////////////////////////////////////////////////////////////////////////////
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// class template Tuple
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// Implements a tuple class that holds a number of values and provides field
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// access to them via the Field function (below)
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////////////////////////////////////////////////////////////////////////////////
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template <class TList>
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struct Tuple : public GenScatterHierarchy<TList, TupleUnit>
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{
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};
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////////////////////////////////////////////////////////////////////////////////
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// helper class template FieldHelper
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// See Field below
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////////////////////////////////////////////////////////////////////////////////
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//### BCB: the problem of not treating enum as bool value, like in MultiMethods
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template <int flag, typename T, typename U>
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struct IntSelect
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{
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typedef T Result;
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};
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template <typename T, typename U>
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struct IntSelect<0, T, U>
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{
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typedef U Result;
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};
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template <class H, unsigned int i> struct FieldHelper;
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template <class H>
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struct FieldHelper<H, 0>
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{
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typedef typename H::TList::Head ElementType;
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typedef typename H::template Rebind<ElementType>::Result UnitType;
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enum
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{
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isTuple = Conversion<UnitType, TupleUnit<ElementType> >::sameType,
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isConst = TypeTraits<H>::isConst
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};
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typedef const typename H::LeftBase ConstLeftBase;
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typedef typename IntSelect<isConst, ConstLeftBase,
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typename H::LeftBase>::Result LeftBase;
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typedef typename IntSelect<isTuple, ElementType,
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UnitType>::Result UnqualifiedResultType;
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typedef typename IntSelect<isConst, const UnqualifiedResultType,
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UnqualifiedResultType>::Result ResultType;
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static ResultType& Do(H& obj)
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{
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LeftBase& leftBase = obj;
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return leftBase;
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}
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};
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template <class H, unsigned int i>
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struct FieldHelper
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{
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typedef typename TL::TypeAt<typename H::TList, i>::Result ElementType;
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typedef typename H::template Rebind<ElementType>::Result UnitType;
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enum
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{
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isTuple = Conversion<UnitType, TupleUnit<ElementType> >::sameType,
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isConst = TypeTraits<H>::isConst
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};
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typedef const typename H::RightBase ConstRightBase;
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typedef typename IntSelect<isConst, ConstRightBase,
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typename H::RightBase>::Result RightBase;
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typedef typename IntSelect<isTuple, ElementType,
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UnitType>::Result UnqualifiedResultType;
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typedef typename IntSelect<isConst, const UnqualifiedResultType,
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UnqualifiedResultType>::Result ResultType;
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static ResultType& Do(H& obj)
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{
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RightBase& rightBase = obj;
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return FieldHelper<RightBase, i - 1>::Do(rightBase);
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}
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};
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////////////////////////////////////////////////////////////////////////////////
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// function template Field
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// Accesses a field in an object of a type generated with GenScatterHierarchy
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// Invocation (obj is an object of a type H generated with GenScatterHierarchy,
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// i is the index of a type in the typelist used to generate H):
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// Field<i>(obj)
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// returns a reference to Unit<T>, where Unit is the template used to generate H
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// and T is the i-th type in the typelist
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////////////////////////////////////////////////////////////////////////////////
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template <int i, class H>
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typename FieldHelper<H, i>::ResultType&
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Field(H& obj)
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{
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return FieldHelper<H, i>::Do(obj);
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}
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// template <int i, class H>
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// const typename FieldHelper<H, i>::ResultType&
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// Field(const H& obj)
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// {
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// return FieldHelper<H, i>::Do(obj);
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// }
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////////////////////////////////////////////////////////////////////////////////
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// class template GenLinearHierarchy
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// Generates a linear hierarchy starting from a typelist and a template
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// Invocation (TList is a typelist, Model is a template of two args):
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// GenScatterHierarchy<TList, Model>
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////////////////////////////////////////////////////////////////////////////////
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template
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<
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class TList,
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template <class AtomicType, class Base> class Unit,
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class Root = EmptyType
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>
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class GenLinearHierarchy;
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template
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<
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class T1,
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class T2,
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template <class, class> class Unit,
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class Root
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>
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class GenLinearHierarchy<Typelist<T1, T2>, Unit, Root>
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: public Unit< T1, GenLinearHierarchy<T2, Unit, Root> >
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{
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};
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template
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<
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class T,
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template <class, class> class Unit,
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class Root
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>
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class GenLinearHierarchy<Typelist<T, NullType>, Unit, Root>
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: public Unit<T, Root>
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{
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};
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} // namespace Loki
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////////////////////////////////////////////////////////////////////////////////
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// Change log:
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// June 20, 2001: ported by Nick Thurn to gcc 2.95.3. Kudos, Nick!!!
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// July 16, 2002: Ported by Terje Sletteb<65> and Pavel Vozenilek to BCC 5.6
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////////////////////////////////////////////////////////////////////////////////
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#endif // HIERARCHYGENERATORS_INC_
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