Re: [boost] generating unique ordinal value at compile time

From: Matthias Schabel (boost_at_[hidden])
Date: 2007-03-01 14:25:58

> But wait, there is hope: you can do this:
>
> ////////
>
> template<class A>
> struct ordinal  {
>        void * tag() {
>           static int const tag_;
>           return &tag_;
>       }
>        template<class B>
>        bool operator<(ordinal<B> const& other) {
>                return std::less<void*>(tag(), other.tag());
>        }
> };
>
> //////
>
> This solution should also be MT safe.

Unfortunately, this doesn't function at compile-time.
That is, what I really want to be able to do is:

struct system1 : ordinal<...> { };
struct system2 : ordinal<...> { };
struct system3 : ordinal<...> { };

typedef mpl::list<system2,system3,system1>	list_type;
typedef mpl::sort<list_type>::type			sorted_list_type;

where mpl::less<> can be defined for ordinal<...>

It seems like a hard (maybe impossible) problem...

Matthias

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