Re: [Boost-users] Needs advices on design ( mpl or processor )

Subject: Re: [Boost-users] Needs advices on design ( mpl or processor )
From: Larry Evans (cppljevans_at_[hidden])
Date: 2012-01-08 13:32:19

On 01/07/12 17:28, Larry Evans wrote:
> On 01/07/12 02:42, Allan Nielsen wrote:
[snip]
>> void example1()
>> {
>>     // As you see, the expresions for calculating the offset get quite long,
>>     // and are not easy to maintain.
> 
> Here's where I don't understand why the calculation are done outside
> the temple and then passed as args to the template.
> Why not have a template do the calculations and accumulate the results,
> somewhat like mpl::fold or the code I posted earlier?
> 
>>     C< CompressedEnum<tagA, 1>,
>>
>>        CompressedEnum<tagB, CompressedEnum<tagA, 1>::offset *
>>                             CompressedEnum<tagA, 1>::size >,
>>
>>        CompressedEnum<tagC,
>>
>>             CompressedEnum<tagB, CompressedEnum<tagA, 1>::offset *
>>                                  CompressedEnum<tagA, 1>::size >::offset
>>             *
>>             CompressedEnum<tagB, CompressedEnum<tagA, 1>::offset *
>>                                  CompressedEnum<tagA, 1>::size >::size
>>        >
>>     > c1;
>>
>>
>> }
>>
[snip]
The attached code produces output:

:eos_t::offset=9
:get_ol(T1)=2
:get_ol(T2)=0
:get_ol(T3)=0
:get<T3>=0
putting:
:get<T1>=0
:get<T2>=1
:get<T3>=2

The output before the putting: lines is caused by the obviously
erroneous initialization of the buffer (no Enum e's stored in
the buffer, only unsigned ints).  The output after the putting: lines
shows the effect of the put<Tag,Enum>(Enum e).

However, be warned! I'm not sure all the casting within the get_ol
and put_ol is portable.

Is this about what you want?

I've looked briefly at Vicente's bit_mask library and it looks
more complicated; however, that extra complication is probably
because it provides extra capabilities.

HTH.

-Larry