Re: [boost] [TTI] Review

Subject: Re: [boost] [TTI] Review
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-07-11 21:11:26

On 7/11/2011 7:03 PM, Edward Diener wrote:
> On 7/11/2011 6:25 PM, lcaminiti wrote:
>>
>> Edward Diener-3 wrote:
>>>
>>> On 7/11/2011 5:02 PM, lcaminiti wrote:
>>>>
>>>> Edward Diener-3 wrote:
>>>>>
>>>>> On 7/11/2011 2:45 PM, Joel falcou wrote:
>>>>>> See :
>>>>>>
>>>>>> https://github.com/MetaScale/nt2/blob/master/modules/sdk/include/nt2/sdk/details/preprocessor.hpp
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> for the file, line 85 and after.
>>>>>>
>>>>>> The point is it works without variadics
>>>>>
>>>>> Line 87: #define NT2_PP_DETAILS_STRIP_PARENS_I(...) 1,1
>>>>> Line 91: #define NT2_PP_DETAILS_TEST_ARITY_I(a,b,c,...) c
>>>>> Line 96: #define NT2_PP_DETAILS_MAYBE_STRIP_PARENS_2_I(...)
>>>>> __VA_ARGS__
>>>>>
>>>>> Clearly it needs variadic macro support.
>>>>>
>>>>> I have already added a REMOVE_PARENS ( the equivalent to
>>>>> NT2_PP_STRIP(X)
>>>>> in your URL above ) to a proposed addition to pp-lib which I am
>>>>> discussing with Paul Mensonides, based on the updated variadic macro
>>>>> support on which both of us worked and which is now in the Boost
>>>>> trunk.
>>>>>
>>>>> My point is also that I may well be able to simplify the
>>>>> BOOST_TTI_TEMPLATE macros in TTI using variadic macro support
>>>>> techniques, as Lorenzo suggested, but I do not feel correct in
>>>>> dropping
>>>>> macro support support for compilers which do not support variadic
>>>>> macros
>>>>> although I understand there are few of them left.
>>>>>
>>>>
>>>> I will later reply to all your comments on my review but let me quickly
>>>> clarify a couple of things.
>>>>
>>>> My suggestion was to have the *same* macro TTI_TEMPLATE handle *both*
>>>> variadics tupletes and sequences.
>>>
>>> I did understand it, and I am willing to do that, but of course it needs
>>> variadic macro support in the compiler. But what do you think I should
>>> do if the compiler does not support variadic macros ? The possibilities
>>> are:
>>>
>>
>> I was trying to say for compilers without variaidics (detected by
>> BOOST_NO_VARIADIC_MACROS) you can do:
>>
>> TTI_TEMPLATE(trait, [tpl_signature_seq_ {class | struct}] name)
>>
>> And for compilers with variadics you can do:
>>
>> TTI_TEMPLATE(trait, [{tpl_signature_seq_ | tpl_signature_va_} {class |
>> struct}] name)
>>
>> Can't you? (Am I missing something?)
>
> I do not want to stick the tpl-signature as a prefix sequence to the
> name. It is ugly and confusing. For some reason you like this sort of
> thing but I find it poor. Furthermore having to extract the template
> parameters from the 'name' itself may be undoable even with varaiadic
> macros much less with only non-variadic macros.

After thinking about this, and calming down a bit ( my apologies for 
getting emotional above ), it may be possible, even without variadic 
macros, to distinguish between:

TTI_TEMPLATE(name)

and

TTI_TEMPLATE((pp-seq) name)

as well as extracting both the pp-seq and the name separately from the 
second form. Still I will probably opt for:

TTI_TEMPLATE(name,BOOST_PP_NIL)

or

TTI_TEMPLATE(name,(pp-seq))

to distinguish between the two for non-variadic macros. I really do not 
like the idea of prepending the name being looked for with the template 
parameters in a single macro argument.