From: http://*.com/questions/1708458/template-metaprogram-converting-type-to-unique-number
template <class Prev, class This> class TypeList { public: enum { position = (Prev::position) + 1, }; }; template <> class TypeList<void, void> { public: enum { position = 0, }; }; #include <iostream> int main() { typedef TypeList< void, void> base; // base typedef TypeList< base, double> t2; // position is unique id for double typedef TypeList< t2, char > t3; // position is unique id for char std::cout << "T1 Posn: " << base::position << std::endl; std::cout << "T2 Posn: " << t2::position << std::endl; std::cout << "T3 Posn: " << t3::position << std::endl; }
确实是非常巧妙的方法。这个方法在Andrei Alexandrescu的《Modern C++ Design》上有详细说明。
这本书在豆瓣上的评分高达9.0,虽然比不上《The C Programming Language》的9.5,但却比Herb
Sutter的《Exceptional
C++》的8.5分要高上不少。