Question

I.e. I got 2 specialized types of:

template <class Type, class Base> struct Instruction {};

to compile-time-select the appropriate type from within a type list.

like:

template <class Base> struct Instruction<Int2Type<Add_Type>, Base > 
{
   void add() {}
};

template <class Base> struct Instruction<Int2Type<Mul_Type>, Base > :
       Instruction<Int2Type<Add_Type>, Base >
{
   void mul() 
   {
      add(); ???? <== not working (not resolved)
   }
};

What’s the solution for this?

Thank you

Martin

Answer 1

add() doesn’t appear to depend on any template parameters (it’s not a “dependent name”), so the compiler doesn’t search for it in the templated base class.

One way to make it clear to the compiler that add() is supposed to be a member function/dependent name, is to explicitly specify this-> when you use the function:

void mul() 
{
   this->add();
}

this implicitly depends on the template parameters, which makes add a dependent name that is looked up in the templated base class.

See also this entry of the C++ FAQ lite, and the next/previous ones.