Example tagged type structure

tagval.h

#ifndef TAGVAL_H__
#define TAGVAL_T__

#include <typeinfo>

struct tagval_t {

    tagval_t(int v): type_(typeid(int)), int_(v) {}
    tagval_t(float v): type_(typeid(float)), float_(v) {}
    tagval_t(const char *v): type_(typeid(const char *)), cstr_(v) {}

    template <typename type_t>
    bool is_a() const {
        return typeid(type_t) == type_;
    }

    template <typename type_t>
    type_t &get() {
        assert(is_a<type_t>());
        return int_;
    }

    template <typename type_t>
    const type_t &get() const {
        assert(is_a<type_t>());
        return int_;
    }

protected:
    union {
        int int_;
        float float_;
        const char *cstr_;
    };

    const std::type_info &type_;
};

#endif // TAGVAL_H__