Re: [boost] [TTI] Review

Subject: Re: [boost] [TTI] Review
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-07-11 19:03:14

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.

However, as you suggested, I can do:

TTI_TEMPLATE(name,pp-seq-or-variadic-template-parameters)

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.

Eddie