条款48：认识template元编

template<unsigned n> // general case: the value of struct Factorial { // Factorial<n> is n times the value // of Factorial<n-1> enum { value = n * Factorial<n-1>::value }; }; template<> // special case: the value of struct Factorial<0> { // Factorial<0> is 1 enum { value = 1 }; }; 

其余没太看懂。。。