Re: [boost] Named Template Parameters

From: David A. Greene (greened_at_[hidden])
Date: 2002-04-06 11:11:43

Gennadiy Rozental wrote:

>>I'm wondering if it would be possible to create a
>>generic library to provide named template parameters.
>>Is this a worthwhile endeavor?  Of course a lot of
>>code exists in the iterator_adaptor detail namespace,
>>but it is tied to the specific policies that
>>iterator_adaptor uses.

> I also think that named template parameters worth separating into library. 
> It brings valueable functionality that could be reused.

I can think of two different solutions to the problem.  The first
is the approach takn by iterator_adaptor.  The second (which I am
investigating now) involves aggregating the policies into a typelist
and then doing a key search to find which policies have been
specified (via tags _a_la_ iterator_adaptor).  The typelist
approach has the following advantages:

   - Fewer template parameters
   - Backward compatability if/when policies are added or removed

The second point really leads me to think that a typelist approach
might be the way to go.  Can anyone argue for the method used by
iterator_adaptor?  I want to make sure I'm not missing something
important.  These aren't mutually exclusive, either -- I'll probably
have fun working on both.  :)

                        -Dave

-- 
"Some little people have music in them, but Fats, he was all music,
  and you know how big he was."  --  James P. Johnson