Re: [boost] [proto] another problem w/ terminal matching

From: Eric Niebler (eric_at_[hidden])
Date: 2007-06-16 02:02:22

Eric Niebler wrote:
> Maurizio Vitale wrote:
>> In the code included, I define a class, K_aux, which inherits from meta_expression<typename proto::terminal<K<mpl::int_<N> >,
>> Normally, objects of type K_aux match a pattern terminal<K<proto::_> >. I'm still fuzzy on why two layers of the type are
>> skipped, but I'm fine with it.
>>
>> Now, if K_aux defines a type named type (e.g. effectively becoming a nullary metafunction) the pattern doesn't match anymore.
> 
> 
> Yep, I've known about this gotcha for a while and have been meaning to 
> fix it before anybody noticed, but you beat me to it. :-P Proto uses the 
> nested type named "type" to mean "the type of this expression", which 
> was fine before proto::extends<> existed, but is dangerous and stupid 
> once people start extending expression types. I'm sorry. Basically, I 
> need to change all the nested types that Proto accesses to be 
> proto-specific. So "type" becomes "proto_type", "tag_type" becomes 
> "proto_tag", and even "arg0_type" becomes "proto_arg0", etc. This is a 
> major breaking change, but it has to be done, and the sooner the better. 
> Darn.

This bug should now be fixed. This involved a massive number of breaking 
renames, so I think this should probably break just about everybody. Sorry.

The following Proto expression nested types/members have been renamed:

   type                    -> proto_base_expr
   tag_type                -> proto_tag
   args                    -> proto_args
   arity                   -> proto_arity
   domain                  -> proto_domain
   arg0_type               -> proto_arg0
   arg1_type               -> proto_arg1
   ...                        ...
   boost_proto_expr_type_  -> proto_derived_expr
   cast()                  -> proto_base()

In addition, there used to be a "proto::trans" namespace alias for 
proto::transform, and I've remove that. Bad idea. Gotta say "transform" 
now, or else create your own alias.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com
The Astoria Seminar ==> http://www.astoriaseminar.com