Loki库读解-扩展TypeList：Typelist生成器、MaxSizeOf
Loki中的TYPELIST_**宏还是太难用了，因为无法支持不定参数。
借鉴于BOOST中的Tuple的想法，实现了这个Typelist_Maker：
template<class T1 = NullType, class T2 = NullType, class T3
= NullType, class T4 = NullType, class T5 = NullType,
class T6 = NullType,
class T7 = NullType, class T8 = NullType, class T9 = NullType,
class T10 = NullType,
class T11 = NullType, class T12
= NullType, class T13 = NullType, class T14 = NullType, class T15 = NullType,
class T16 = NullType, class T17
= NullType, class T18 = NullType, class T19 = NullType, class T20 = NullType,
class T21 = NullType, class T22
= NullType, class T23 = NullType, class T24 = NullType, class T25 = NullType,
class T26 = NullType, class T27
= NullType, class T28 = NullType, class T29 = NullType, class T30 = NullType,
class T31 = NullType, class T32
= NullType, class T33 = NullType, class T34 = NullType, class T35 = NullType,
class T36 = NullType, class T37
= NullType, class T38 = NullType, class T39 = NullType, class T40 = NullType,
class T41 = NullType, class T42
= NullType, class T43 = NullType, class T44 = NullType, class T45 = NullType,
class T46 = NullType, class T47
= NullType, class T48 = NullType, class T49 = NullType, class T50 = NullType>
struct Typelist_Maker
{
private:
typedef TYPELIST_50(T1, T2, T3, T4, T5, T6, T7, T8, T9, T10,
T11, T12, T13, T14, T15, T16, T17, T18, T19, T20,
T21, T22, T23, T24, T25, T26, T27, T28, T29, T30,
T31, T32, T33, T34, T35, T36, T37, T38, T39, T40,
T41, T42, T43, T44, T45, T46, T47, T48, T49, T50) TmpList;
public:
typedef typename EraseAll<TmpList, NullType>::Result Result;
};
这下，世界会清净多了。
然后一个小扩展是MaxSizeOf，取一组类型中的最大大小。
传统方法是使用union的，当然是感觉不爽了。
template<class Tlist>
struct MaxSizeOf;
template<>
struct MaxSizeOf<NullType>
{
enum {value = 0};
};
template<class Head, class Tail>
struct MaxSizeOf<Typelist<Head, Tail> >
{
private:
enum {MaxSizeOfTail = MaxSizeOf<Tail>::value};
public:
enum {value = (sizeof(Head) > MaxSizeOfTail ? sizeof(Head) :
MaxSizeOfTail)};
};