CODEWITHSUNDEEP
c++templatesc++11partial-specialization
AlwaysLearning
AlwaysLearning

Reputation: 8001

A template that accepts only pointer type arguments

After seeing that a template can be partially specialized for reference or pointer types, I was wondering whether I can write a template that accepts only a pointer type to start with. This is my attempt:

template <typename T*>
struct MyTemplate{};

int main() {
    MyTemplate<int *> c;
    (void)c;
    return 0;
}

This does not compile. How should it be modified? (i.e. if what I am trying to accomplish is at all possible)

Upvotes: 14

Views: 3173

Answers (1)

Jarod42
Jarod42

Reputation: 217075

You may use partial specialization:

template <typename T> struct MyTemplate; // Declaration

template <typename T> struct MyTemplate<T*> // Specialization
{
};

or use static_assert

template <typename T> struct MyTemplate
{
    static_assert(std::is_pointer<T>::value, "Expected a pointer");

    // T = value_type*
    using value_type = std::remove_pointer_t<T>;
};

In C++20, you might use constraint:

template <typename T>
requires (std::is_pointer_v<T>)
struct MyTemplate
{
};

Upvotes: 21

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