C++: specifying a base class for a template parameter

I need to design a framework that computes the result of a divide-et-conquer algorithm in parallel. In order to use the framework, the user needs to specify somehow the procedure that implements the "divide" phase (a function from T to T), the "conquer" phase (a function from D to D) and T and D themselves.

I've thought it would be nice to define two abstract classes, BaseDivide and BaseConquer, which declares a pure virtual method compute with the right types: that way I have a type which implements a well-defined concept (from the point of view of the framework) with the user-definable function included by means of derivation of the abstract classes.

I've thought to use templates to pass the type开发者_开发技巧s to the framework, so the user doesn't have to instantiate them in order to use the framework, so something like that:

template <typename T, typename D, typename Divide, typename Conquer> 
D compute(T arg);

My problem is that I want that Divide and Conquer to be derived types of BaseDivide and BaseConquer: there is a way to enforce it at compile time? Also: do you think I can achieve a similar result with a cleaner design?

---

You could create the base classes like this:

struct BaseDivide {
    enum EnumDiv { derivedFromBaseDivide = true };
}

template <typename T, typename D, typename Divide, typename Conquer> 
    static_assert(D::derivedFromBaseDivide);
    D compute(T arg);

What is the purpose of the additional Divide and Conquer template parameters? Are you sure you need them?

---

Use Boost.EnabelIf to trigger SFINAE when your types don't fulfill your requirement. Checking if T is derived from U is doen with boost::is_base_of :

#include <boost/type_traits/is_base_of.hpp>
#include <boost/enable_if.hpp>

template <typename T, typename D, typename Divide, typename Conquer> 
typename boost::
enable_if_c< boost::is_base_of<BaseDivide,Divide>::value 
          && boost::is_base_of<BaseConquer,Conquer>::value
          ,D
          >::type
compute(T arg);

---

You don't need to use templates for this purpose. Instead, you can use pointers to BaseDivide and BaseConquer objects, and polymorphism will do the job for you.