Re: [Boost-users] [boost] [switch_] Case Concept [ was Re: formal review of Switch library...]

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-01-12 15:33:51

AMDG

Joel de Guzman wrote:
> Valid Expressions:
>
>      Expression              Semantics
>      ---------- 
> --------------------------------------------------------
>      C::labels               An MPL Sequence of Integral Constants
>   

I think that a case should only have a single label.  Allowing multiple 
labels
makes the implementation harder without adding any significant utility.  
See below.

>      case_<I>(f)             Returns a Case object with supplied
> <snip more generators>
>   

These can return fusion sequences of cases instead of plain cases.
This has the additional benefit that switch_ can be specified as taking
a fusion sequence of cases, without having to handle a single case 
specially.

>      default_(f)             Returns a Case object with an empty labels list.
>                              forwarding to the encapsulated function object f.
>   

 From the standpoint of the implementor of switch_, how do I figure out 
which
Case is the default?

>    * case_c and case_range_c are simple shortcuts. The type of
>      integral constant is int. The actual type can be casted to
>      the actual switch parameter. I think this is safe

Since the value is known at compile time the cast can be checked at 
compile time to detect overflow.

In Christ,
Steven Watanabe