[boost] Unicode: what kind of binary compatibility do we want?

Subject: [boost] Unicode: what kind of binary compatibility do we want?
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2009-06-01 23:09:05

As I am finishing putting property look-up together for the Unicode 
library GSoC, I am wondering what kind of binary compatibility it should 
aim for.

The work from Graham Barnett back in 2005 defined an abstract base class 
with virtual functions for every unicode-related feature but I believe 
that's overkill.

Basically, the current property design I have is like this

struct some_property
{
     enum type
     {
         some_default,
         some_value1,
         some_value2,
         ...
         _count;
     }
};

some_property::type get_some_property(char32 ch);

With get_some_property a simple look-up in the table, but the table 
layout being version dependent it would need to be in the library TUs.

However, a new version of the library may return a value that is not 
within the enum.

Should it then work like this?

some_property::type get_some_property(char32 ch)
{
     some_property::type p = get_some_property_impl(ch);
     if(p >= some_property::_count)
        return some_property::some_default;
     return p;
}

some_property::type get_some_property_impl(char32 ch);

Is that suitable? Or do we want more/less flexibility?

Apart from that, expect a documentation update by the end of the week.