Re: [Boost-users] [switch_] Compound Cases [was Case Concept]

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-01-14 13:49:22

AMDG

Joel de Guzman wrote:
> Tobias Schwinger wrote:
>
>   
>>>> (c0,c1,...,cN) being just another 'Case' rather than a 'Sequence'.
>>>>         
>>> o..k... Hmm.. so how would the resulting case object for this
>>> expression look like:
>>>
>>>      case_c<1>(f1), case_c<2>(f2)
>>>
>>> ?
>>>       
>>      template< class SeqCases >
>>      struct sequenced_case
>>      {
>> <snip>
>>     
>
> Sounds good to me! I like it. So, this involves the variation where
> a case has an MPL sequence of labels. I knew there's something in
> that that I like. Intuition, I guess. That is also why I use the
> name case_ regardless of number. A compound case is just another
> case anyway. Does not matter how many labels it serves.
>
> Not sure how, implementation-wise, this works for Steven. Steven?
> If this pans out, I'll refine the concept one more time.
>   

It's trivial to implement:

#define BOOST_SWITCH_CASE(z, n, data)\
    case mpl::at_c<typename C::labels, n>::type::value: 
return(c.apply<R>(mpl::int_<n>()));

My concern is
1) fall-through can't easily be added to the interface.
2) It seems like just another interface for a fusion sequence.
    Is sequenced_case to be public?  If so, we need another
    concept for its interface...

In Christ,
Steven Watanabe