Re: [boost] [TTI] Review

Subject: Re: [boost] [TTI] Review
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-07-11 21:33:07

On 7/11/2011 9:17 PM, Lorenzo Caminiti wrote:
> On Mon, Jul 11, 2011 at 7:03 PM, Edward Diener<eldiener_at_[hidden]>  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.
>>
>> You have fallen in love with this sort of thing, perhaps because you have
>> had to do something similar your 'local' library, but I will opt for a
>> simpler and clearer way, even if it means a few extra macro names.
>
> Fair enough. My comment #5 was just a NOTE so I actually really don't
> feel strongly about it (and "love" would instead be a strong feeling
> ;) ). If I'm the only one suggesting this syntax, you should probably
> ignore it.
>
>> However, as you suggested, I can do:
>>
>> TTI_TEMPLATE(name,pp-seq-or-variadic-template-parameters)
>
> Sure, my comment #6 (removing VM macros) is independent from my
> comment #5 (removing CHECK_PARAMS macros).
>
>> with variadic parameters support, and will look to implement a single macro
>> on that side rather than both TTI_TEMPLATE and TTI_TEMPLATE_CHECK_PARAMS.
>
> I'm not sure about this... wouldn't you expect the macros to be
> symmetric with and without variadics? In other words, if there is a
> CHECK_PARAMS without variadics, I would expect it to be a CHECK_PARAMS
> also with variadics. That is because CHECK_PARAMS does not
> semantically have anything to do with variadics, it is just "the macro
> you use when you specify the template parameters" (variadics or not).

As my second reply explains I might be able to do a single nonvariadic 
macro of either:

TTI_TEMPLATE(name,BOOST_PP_NIL)

and

TTI_TEMPLATE(name,(pp-seq))

to distinguish between the two. I will look into it.

Eddie