How to avoid repeating the whole class template when only one member specialization is needed

Question

Suppose you have:

template<class T>
class A {
  template<class T1> 
  void foo(const T1& t1) {}

  //
  // Lots of other definitions (all templated)
  // 
};

and you would like to specialize foo(const T1&) but only for a specialized A<bool>. Like this:

template<>
class A<bool> {
  template<class T1> 
  void foo(const T1& t1) {
    // Code for specialized A<boo>::foo
  }

  //
  // Repeating the former definitions, how to avoid this ??
  // 
};

But to get this to work I have to duplicate all the code that is defined in the class template class A and include it again in class A<bool>.

I tried to define only the member specialization:

template<>
void A<bool>::template<class T1> foo(const T1&) {}

Neither does this work:

template <class T1> void A<bool>::foo(const T1&) {}

But the compiler doesn't like it. What's the way to deal with this code duplication?

Answer 1

Syntax? See this answer. Try:

template<>
template<typename T1>
void A<bool>::foo(const T1&){}

You certainly don't need to copy the whole class template.