Typelists(三)

类型排序准则(将最深派生放在最前方)

Typelists3.h

#include "../型别选择/select.h"//for template<class If, class Then, class Else> struct Select;
#include "../编译期间侦测可转换性和继承性/Conversion.h"//for #define DERIVE_BASE_CLASS
#include "Typelists2.h"
//从Tlist中找到T的最深派生类
template<class TList, class T> struct MostDerived;
/*****普遍情况*****/
template<class First, class Second, class T>
struct MostDerived<TypePair<First, Second>, T>
{
    //Second部分的最深派生类
    typedef typename MostDerived<Second, T>::Result Cadidate;
    //和First比较，取更深的派生类
    typedef typename Select<DERIVE_BASE_CLASS(First, Cadidate), First, Cadidate>::Result Result;
};
/*****边界情况*****/
//如果是空链表就是它本身
template<class T>
struct MostDerived<NullType, T>
{
    typedef T Result;
};

//将派生类移动到最前方
template<class TList> struct DeriveToFront;
/*****普遍情况*****/
template<class First, class Second>
struct DeriveToFront<TypePair<First, Second>>
{
    //找到First的最深继承子类
    typedef typename MostDerived<Second, First>::Result DerivedClass;
    //替换在Second中替换这个类
    typedef typename Replace<Second, DerivedClass, First>::Result NewSecond;
    //生成新的结果
    typedef TypePair<DerivedClass, NewSecond> Result;
};
/*****边界情况*****/
template<>
struct DeriveToFront<NullType>
{
    typedef NullType Result;
};

Typelists3.cpp

#include <iostream>
using namespace std;
#include "Typelists3.h"
struct Base{};
struct DeriveA:Base{};
struct DeriveB:Base{};
struct DeriveBA:DeriveB{};
int main()
{
    typedef Typelists_4(Base, DeriveA, DeriveB, DeriveBA) OriginalList;
    cout << typeid(TypeAt<OriginalList, 0>::Result).name() << endl;
    cout << typeid(TypeAt<OriginalList, 1>::Result).name() << endl;
    cout << typeid(TypeAt<OriginalList, 2>::Result).name() << endl;
    cout << typeid(TypeAt<OriginalList, 3>::Result).name() << endl << endl;

    //2005的傻子编译器对后者会给出报错
    /*static_cast<unsigned>(Conversion<Base*, const DeriveA*>::exist && !Conversion<DeriveA*, const void*>::sameType);
                   unsigned(Conversion<Base*, const DeriveA*>::exist && !Conversion<DeriveA*, const void*>::sameType);*/
    typedef DeriveToFront<OriginalList>::Result CurrentList;
    cout << typeid(TypeAt<CurrentList, 0>::Result).name() << endl;
    cout << typeid(TypeAt<CurrentList, 1>::Result).name() << endl;
    cout << typeid(TypeAt<CurrentList, 2>::Result).name() << endl;
    cout << typeid(TypeAt<CurrentList, 3>::Result).name() << endl << endl;
}
/*
struct Base
struct DeriveA
struct DeriveB
struct DeriveBA

struct DeriveBA
struct DeriveA
struct DeriveB
struct Base
*/