Using templated class in templated class c++

Question

I have to implement a data structure in multiple different ways, each of which should be compatible with using multiple data types.

I then have to make a class that can test all of these implementations using different data types.

Example:

Testobject obj = Testobject<DatastructType1<int>>();
Testobject obj2 = Testobject<DatastructType2<float>>();

I have tried multiple ways to use the correct syntax for the Testobject class.

template <typename T, typename U>
class Testobject {
    public:
        Testobject();

    private:
        T<U> data;

};

It looks like this now, but instead of this first line I have also tried the following:

template <typename T <typename U>>

template <typename T, template <typename> class U>>

template <template <typename T> class U>

So basically I'm wondering what the right syntax is.

EDIT: my lecturer just simplified the assignment, so this is no longer necessary. However, if anyone has a solution, I'm still curious.

Jarod42 · Accepted Answer · 2021-09-17 19:06:17Z

2

You have several choices depending of the syntax expected:

template <typename T>
class Testobject {
public:
    Testobject();

private:
    T data;
};

Testobject obj = Testobject<DatastructType1<int>>();
Testobject obj2 = Testobject<DatastructType2<float>>();

or

template <template <typename> class C, typename T>
class Testobject
{
public:
    Testobject();

private:
    C<T> data;
};

Testobject obj = Testobject<DatastructType1, int>();
Testobject obj2 = Testobject<DatastructType2, float>();

A variant of first snippet, with partial specialization:

template <typename T> class Testobject;

template <template <typename> class C, typename T>
class Testobject<C<T>>
{
public:
    Testobject();

private:
    C<T> data;
};

Testobject obj = Testobject<DatastructType1<int>>();
Testobject obj2 = Testobject<DatastructType2<float>>();

answered Sep 17, 2021 at 19:06

Jarod42

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