Re: [boost] [Boost-users] formal review of Switch library ends tomorrow (Wednesday, January 9th) - reviews needed

From: Joel de Guzman (joel_at_[hidden])
Date: 2008-01-11 00:27:07

Joel de Guzman wrote:
> Stjepan Rajko wrote:
> 
>> "A" seems ideal for this use case.  I have trouble seeing how to use
>> "B" for it (easily) without making it so that the index is passed to
>> the function object and allowing something like case<range>(...).  But
>> I might not be seeing all the possibilities.  How can I implement this
>> using "B"?
> 
> Ok, you are right. There is indeed no way to "bind" the
> case (a compile time constant (e.g. mpl::int_)). It is
> indeed crucial to have the case passed as the argument.
> Once we have it, then (I'm inventing some more syntax):
> 
>      switch_<RT>(n)(all_cases(f));

Heh, that won't work. You really need to supply the cases:

     switch_<RT>(n)(case_range<From, To>(f));

> Come to think of it, this is the only solution needed to map
> an A-style all-in-one-function to B! No need for Fusion, no
> need for extra infrastructure. All we need to do is pass
> the case as an argument to f.
> 
> The key point (and one that I am trying to capture) is to define
> the Concept of a Case. That is crucial. Once that's done, everything
> flows naturally.

I'll try to come up with a complete interface proposal that
will encompass all use cases. It will be lightweight (no need
for extra infrastructure) and efficient. I believe it can
be done.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net