Question

I am thinking about using curiously recurring template pattern for my application. However, I would like the classes to operate on the user defined types. I would like to understand if it is possible to create a structure similar to the one shown below:

template <class T_leaftype>
class BaseTrajectoryPoint {
};


template <class MyType>
class MyTrajectoryPoint: public BaseTrajectoryPoint<MyTrajectoryPoint> {
    private:    
        MyType A;
};

The code above fails to compile with the following error:

type/value mismatch at argument 1 in template parameter list for ‘template class BaseTrajectoryPoint’

Are there any alternative ways of approaching the problem? I would like to use static polymorphism, but I would prefer to define all possible methods in the base class.

Answer 1

template <class T_leaftype>
class BaseTrajectoryPoint {
};


template <class MyType>
class MyTrajectoryPoint: public BaseTrajectoryPoint<MyTrajectoryPoint<MyType> > {
    private:    
        MyType A;
};

MyTrajectoryPoint isn’t a type, it’s template; when you pass it as template parameter, it’s seen as template<typename> class T>, not template<class T> – and the latter is what your base class is expecting. But MyTrajectoryPoint<MyType> names a type, so you can use it as template parameter of your base class.

Of course, you can change declaration of BaseTrajectoryPoint to template<template<class> class T_leaftype>, but then you would have to use class template as template parameter, never a complete type.