Re: [boost] BOOST_ENUM proposal

From: Frank Laub (frank.laub_at_[hidden])
Date: 2005-12-09 00:45:26

Thanks a lot for this suggestion. It inspired me to write version 2. In this
approach, the macro expansion only produces a type that contains the
underlying enum and storage(), which contains all the strings. The trick now
is that there is:

template <typename base>
struct safe_enum : base;

The macro now expands:

BOOST_ENUM(Boolean,
    (False)
    (True)
)

to:

    class Boolean_base
    {
    public:
        enum type
        {
            False,
            True,
            size = 2,
            Invalid = -1
        };

    protected:
        typedef boost::array<const char*, (size)+1> array_type;
        static const array_type& storage()
        {
            static const array_type names =
            {
                "False",
                "True",
                "2"
            };
            return names;
        }
    };
    typedef safe_enum<Boolean_base> Boolean;

The Boolean now gets the following methods from safe_enum:
begin()
end()
operator[]
str() (CT and RT versions)
parse()

I was thinking of re-naming the other kind of enum that I had before
(BOOST_ENUM_COMMENTS) to something like BOOST_STRINGTABLE, since that's
really the intention.

I've uploaded v2 to the file vault under Preprocessor Metaprogramming. I'd
love to hear more suggestions or even complaints!

Thanks a ton,
-Frank