Rename std::vector to another class for overloading?

问题

Look at this code.

#include <vector>

template<class ...Args>
using other_vector = std::vector<Args...>;

template<class T>
void f(std::vector<T>& ) {}
template<class T>
void f(other_vector<T>& ) {}

int main()
{
    other_vector<int> b;
    f(b);
    return 0;
}

It does not compile, because f is being redeclared. I totally understand the error. However, I need a second class that behaves like std::vector<T>, but will be seen as a different type, so that overloading, like in the above example, would be legal.

What could I do?

Let the new class have std::vector<T> as a base class. This might work, but one should not inherit from std containers.
Let the new class have a member of type std::vector and then redeclare all functions to redirect to the functions of the member. Sounds like a lot of work.

Any better alternative? C++11 or C++14 allowed.

回答1:

You might try to mess with the allocator:

template<class T>
struct allocator_wrapper : T { using T::T; };

template<class T, class A = std::allocator<T>>
using other_vector = std::vector<T, allocator_wrapper<A>>;

Live example

回答2:

If you need more than one copy, you can make it a template and take an int template arg for "clone number"

回答3:

You may wrap your type as follow:

// N allow to have several 'version' of the same type T
template <typename T, int N = 0>
class WrapperType
{
public:
    WrapperType() = default;
    WrapperType(const WrapperType&) = default;
    WrapperType(WrapperType&&) = default;

    template <typename ... Ts>
    explicit WrapperType(Ts&& ... ts) : t(std::forward<Ts>(ts)...) {}

    // implicit conversion
    // you may prefer make them explicit or use name get().
    operator const T& () const { return t; }
    operator T& () { return t; }

private:
    T t;
};

And so for your case:

template<class T>
using other_vector = WrapperType<std::vector<T>>;

来源：https://stackoverflow.com/questions/20973526/rename-stdvector-to-another-class-for-overloading

标签

c++

c++11

stdvector