Hi, Daniel. This is your example: template <class T> void S::f() { if(g is specialized) // (1) callbacks_ready=true; // else wait for a callback object to be registered } At (1) the runtime detection is used, but "S:g()" was specialized at compile time. Templates are specialized and compiled at compile time, but not runtime. We can't write "if(g is specialized)" - it is impossible to realize it at runtime (and it is senseless). So let me to recommend you some books of H. Sutter and A. Alexandrescu. There are a lot of recommendations about templates, their specializations, overloads, static/dynamic polymorphisms and more. 1st book: [http://www.gotw.ca/publications/xc++s.htm] Pay attention to this chapter of the book: "Item 7: Why Not Specialize Function Templates?" 2nd book; "C++ Coding Standards: 101 Rules, Guidelines, and Best Practices" (authors H. Sutter and A. Alexandrescu) Pay attention to 64, 65, 66 and 67 chapters. I hope you will find some useful ideas about templates in these books. There are also Boost libraries targeted to realize static polymorphism: 1) http://www.boost.org/doc/libs/1_40_0?view=category_Generic 2) http://www.boost.org/doc/libs/1_40_0?view=category_Metaprogramming Best, Andrew.
Slightly OT, but I was hoping someone here might know the magic incantation
(which may involve a Boost library).
Given a template class such as
template <class T> struct S { void f(); void g() { T t(h()); cb(t) } T & h(); boost::function1<void, T &> cb; };
Is there a way to have S.f() behave differently depending on whether S.g() uses the default definition or whether it is specialized for this particular type? This detection needs to occur before S.g() is ever called.
For example, the mere existance of the specialization template <> void S<int>::g() { ... } should trigger special logic in S<int>::f().
Thanks, Daniel P.S. The motivation for this is an attempt to retrofit a callback API that
allows specialization of S.g() or the registration of a boost::function that gets called by the default S.g(). We need to disable callbacks until an actual function is registered via either method. It is easy to dispatch on registration of the boost::function; I don't know how to detect the specialization.