Am 24.03.2016 um 20:34 schrieb Antony Polukhin:
I've improved the implementation, now it has more functionality.
Github repo: https://github.com/apolukhin/magic_get
Changes:
* separate ready-for-inclusion header "magic_get.hpp" that depends only on
C++14 features (noo Boost deps)
* support for nested PODs
* now works with libstdc++ too
* more fundamental types supported
* improved compilation time
* now works with arrays too
* more extensions are allowed
* support for detecting volatile pointers
* added flat_ to public API (flat_get, flat_tuple_size)
* added multiple comments
I found a way to get a type_name type at compile type, i.e. a template
which has a sequence of chars representing the type. This could be added
to boost.type_index and would allow constexpr sorting of types by names
etc. E.g. making boost::variant and boost::variant the same, by ordering the arguments alphabetically. Has lot of
compiler overhead though.
That might also be a workaround for the REGISTER_TYPE thing in you magic
get, though I have to admit: I don't really get how this approach works,
so I don't know.
Here's the code for that (would need some polishing for sure), I've
built it with Gcc 6. Don't know if other compiler play along with that.
#include <iostream>
#include <array>
#include
#include
#include <tuple>
using namespace std;
template
struct char_seq {};
template
struct index_seq
{
};
template
struct append;
template
struct append, Append>
{
using type = index_seq;
};
template
using append_t = typename append::type;
template>
struct make_index_seq
{
typedef typename make_index_seq>::type type;
};
template
struct make_index_seq
{
typedef T type;
};
template
using make_index_seq_t = typename make_index_seq<Size>::type;
template<char c> struct char_entry {};
template<typename T>
struct constexpr_ti
{
template
constexpr static char step()
{
return __PRETTY_FUNCTION__[Index];
}
template
constexpr static auto impl(index_seq * = nullptr)
{
return char_seq();
}
constexpr static auto make()
{
//the 37 is determined by hand
using idx_seq = make_index_seq_t *;
return impl(idx_seq());
}
};
template<typename T>
constexpr auto make_type_idx()
{
return constexpr_ti<T>::make();
}
template
void print(char_seq)
{
std::array arr = {C..., '\0'};
cout << arr.data() << endl;
}
int main()
{
using boost::typeindex::type_id;
constexpr auto x = make_type_idx>();
{
using t = make_index_seq_t<12>;
cout << type_id<t>().pretty_name() << endl;
}
{
using t = decltype(x);
cout << type_id<t>().pretty_name() << endl;
}
print(x);
return 0;
}
