Variadic templates type traits resolution

Assume I have an enum, and I want each enum value to be associated with a certain type. Say the standard type is double, and if I want it to be something else I need to specify it explicitly. Q1: Is this the preferred way to implement such a thing? ``` enum A { v1, v2, v3 }; // for every value of A, the standard type is double template<A a> struct A_info { typedef double type; }; // other types for certain values can be specified using specialization template<> struct A_info<v2> { typedef size_t type; }; ``` Then, assume I have some function template, and I want to call the function depending on the type associated with a value of the enum: ``` template<typename T> void foo() { /* do something */ } template<A a> void bar() { foo< typename A_info<a>::type >(); } ``` This works fine. Now assume, I have another function depending on a variadic template list, and I want to do something similar as above ... ``` template<typename ... T> void foo_multiple() { /* stuff */ } template<A ... a> void bar_multiple() { foo_multiple< /* ??? */ > (); } ``` Q2: How to implement this? Is this possible, anyway?