Can C Store Data of Different Types in a Single Container?

Heterogeneous Containers in C

Question:

The STL container classification graphic suggests that there is no STL container that is both variable size and heterogeneous. Does C lack a solution for storing data of different types?

Answer:

While C containers are typically designed to hold objects of a single type, there are ways to store different types of data:

• Pointers: Use a container of pointers to objects of a common base class, allowing you to store objects of different derived types.
• boost::any: Store objects of any type in a container. This uses a template metaprogramming approach to handle different types safely.
• boost::variant: Similar to boost::any, but requires specifying the allowed types at compile time.

Code Example:

<code class="cpp">#include <list>
#include <boost/any.hpp>

using boost::any_cast;
typedef std::list<boost::any> many;

int main() {
    many values;
    append_int(values, 10);
    append_string(values, "Hello");

    if (is_int(values.front())) {
        int number = any_cast<int>(values.front());
        std::cout << number << std::endl;
    }

    return 0;
}</code>

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