A trailing template-argument can be left unspecified in the template-id naming an explicit function template specialization provided it can be deduced from the function argument type. [ Example:

template<class T> class Array { /* ... */ };
template<class T> void sort(Array<T>& v);

// explicit specialization for sort(Array<int>&)
// with deduced template-argument of type int
template<> void sort(Array<int>&);

 — end example ]