[boost] Re: Small tuple extension

From: Larry Evans (cppljevans_at_[hidden])
Date: 2005-04-27 16:02:41

Replying to self:

On 04/27/2005 11:54 AM, Larry Evans wrote:
[snip]
>>> with enum is clumsy and not type safe.  I.e. a tuple might not map 
>>> the whole enum set enum {a, b, c}, but get<a>(tuple_foo) would still 
>>> compile even if 'a' is not logically part of tuple_foo. Also you are 
> 
> 
> If you've defined the enum and map together, e.g. in the enum_map<i>
> structure, and used them together in enum_mapped, as shown here:
> 
> http://boost-sandbox.sourceforge.net/vault/index.php?&direction=0&order=&directory=cppljevans 
> 

OOPS.  Maybe you meant that although there were, e.g. 3 enumerators in
the enumeration, the map was only defined for 2 or 1 or none.  To be 
concrete, an example would be where enum_map<0> in the above vault code
were:

   template
   <
   >
   struct
enum_map
   < 0
   >
{
       enum
     field_names
     { f_0
     , f_1
     , f_2
     };

       template<field_names FieldName>
       struct
     field_name
     {};

         typedef
       mpl::map
       < mpl::pair<field_name<f_0>, type_i<0> >
       >
     field_map
     ;
};

then I can see your point about "tuple might not map
the whole enum set".