Re: Endorsement, review manager sought for Boost.Describe

From: Peter Dimov (pdimov_at_[hidden])
Date: 2020-09-24 22:13:28

Vinícius dos Santos Oliveira wrore:
> Hi Peter,
>
> could you consider using "compile-time strings" such as Hana's? I don't 
> have much use for a const char* in TMP algorithms.

The descriptor strings are "compile-time". This, for instance, works.

#include <boost/describe.hpp>
#include <boost/mp11.hpp>
#include <cstddef>
#include <array>

using namespace boost::describe;
using namespace boost::mp11;

enum E
{
    v1
};

BOOST_DESCRIBE_ENUM(E, v1)

constexpr std::size_t strlen_( char const * s )
{
    std::size_t n = 0;
    while( *s++ ) ++n;
    return n;
}

constexpr std::size_t hash_value( char const * s )
{
    std::size_t n = 5381;
    while( *s ) n = n * 31 + static_cast<unsigned char>( *s++ );
    return n;
}

template<class D> constexpr auto name_as_array()
{
    constexpr auto n = strlen_(D::name);

    std::array<char, n> r{};

    for( std::size_t i = 0; i < n; ++i )
    {
        r[i] = D::name[i];
    }

    return r;
}

using D = mp_first< describe_enumerators<E> >;

constexpr auto x1 = strlen_( D::name );
constexpr auto x2 = hash_value( D::name );
constexpr auto x3 = name_as_array<D>();