异构POD类型的C ++容器

Question

Is there a form of heterogeneous container, that is able to to store for example different primitive types (such as int , float , double )?

Ultimately I'd like to be able to use the elements in calculations without referring to the type explicitly, for example auto res = a + b , where the operands a and b are elements pulled out of the container and could be of same or different types.

Answer 1

With C++17 you can use std::any with any container. With older C++ versions you can use boost::any .

#include <iostream>
#include <vector>
#include <any>

struct A
{
    int a;
    explicit operator int() const { return a; }
};

struct B
{
    double b;
    explicit operator double() const { return b; }
};

int main()
{
    A a{ 5 };
    B b{ 6.};

    std::vector<std::any> v;
    v.push_back(3 );
    v.push_back(4.);
    v.push_back(a );
    v.push_back(b );

    for (auto const e : v)
    {
        if (e.type() == typeid(double))
            std::cout << std::any_cast<double>(e) << std::endl;

        if (e.type() == typeid(B))
            std::cout << (double)std::any_cast<B>(e) << std::endl;
    }
}