Re: [boost] [TTI] Review

Subject: Re: [boost] [TTI] Review
From: Lorenzo Caminiti (lorcaminiti_at_[hidden])
Date: 2011-07-11 21:17:06

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).

Thanks,
--Lorenzo