Loki的TypeList技术解析 - JAVA

ct TypeAt; template struct TypeAt , 0> { typedef Head Result; }; template struct TypeAt , i> { typedef typename TypeAt ::Result Result; }; //////////////////////////////////////////////////////////////////////////////// // class template TypeAtNonStrict // Finds the type at a given index in a typelist // Invocations (TList is a typelist and index is a compile-time integral // constant): // a) TypeAt ::Result // returns the type in position 'index' in TList, or NullType if index is // out-of-bounds // b) TypeAt ::Result // returns the type in position 'index' in TList, or D if index is out-of-bounds //////////////////////////////////////////////////////////////////////////////// template struct TypeAtNonStrict { typedef DefaultType Result; }; template struct TypeAtNonStrict , 0, DefaultType> { typedef Head Result; }; template struct TypeAtNonStrict , i, DefaultType> { typedef typename TypeAtNonStrict ::Result Result; }; //////////////////////////////////////////////////////////////////////////////// // class template IndexOf // Finds the index of a type in a typelist // Invocation (TList is a typelist and T is a type): // IndexOf ::value // returns the position of T in TList, or NullType if T is not found in TList //////////////////////////////////////////////////////////////////////////////// template struct IndexOf; template struct IndexOf { enum { value = -1 }; }; template struct IndexOf , T> { enum { value = 0 }; }; template struct IndexOf , T> { private: enum { temp = IndexOf ::value }; public: enum { value = (temp == -1 -1 : 1 + temp) }; }; //////////////////////////////////////////////////////////////////////////////// // class template Append // Appends a type or a typelist to another // Invocation (TList is a typelist and T is either a type or a typelist): // Append ::Result // returns a typelist that is TList followed by T and NullType-terminated //////////////////////////////////////////////////////////////////////////////// template struct Append; template <> struct Append { typedef NullType Result; }; template

struct Append { typedef Typelist Result; }; template struct Append > { typedef Typelist Result; }; template struct Append , T> { typedef Typelist ::Result> Result; }; //////////////////////////////////////////////////////////////////////////////// // class template Erase // Erases the first occurence, if any, of a type in a typelist // Invocation (TList is a typelist and T is a type): // Erase ::Result // returns a typelist that is TList without the first occurence of T //////////////////////////////////////////////////////////////////////////////// template struct Erase; template // Specialization 1 struct Erase { typedef NullType Result; }; template // Specialization 2 struct Erase , T> { typedef Tail Result; }; template // Specialization 3 struct Erase , T> { typedef Typelist ::Result> Result; }; //////////////////////////////////////////////////////////////////////////////// // class template EraseAll // Erases all first occurences, if any, of a type in a typelist // Invocation (TList is a typelist and T is a type): // EraseAll ::Result // returns a typelist that is TList without any occurence of T //////////////////////////////////////////////////////////////////////////////// template struct EraseAll; template struct EraseAll { typedef NullType Result; }; template struct EraseAll

Loki的TypeList技术解析(二)