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c#c++templatesgenerics
ido kahana
ido kahana

Reputation: 165

convert generic code from c# to template c++

I try to convert this code (c# code) to c++ code

public abstract class IGID<T>
    where T : IGID<T>

how do i implement such a template condition in c++ ?

Upvotes: 1

Views: 174

Answers (1)

Barry
Barry

Reputation: 302817

The best you could do is throw a static_assert in an empty base class that will fire on construction. You have to delay until use because all the types have to complete before you can do any such checking.

We have our assertion object:

template <typename C>
struct Require {
    Require() {
        static_assert(C::value, "!");
    }
};

It's empty, so adds no overhead. And then we have:

template<typename T>
struct IGID : Require<std::is_base_of<IGID<T>, T>>
{
};

Even though T is incomplete here, we don't check anything until IGID<T> is constructed, so we're okay.

struct A : IGID<A> { }; // okay

But:

struct B : IGID<int> { }; 

main.cpp:8:9: error: static_assert failed "!"
        static_assert(C::value, "!");
        ^             ~~~~~~~~
main.cpp:13:8: note: in instantiation of member function 'Require<std::is_base_of<IGID<int>, int> >::Require' requested here
struct IGID : Require<std::is_base_of<IGID<T>, T>>
       ^

Upvotes: 4

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