Re: [boost] Increasing BOOST_PP_VARIADICS_SIZE

Subject: Re: [boost] Increasing BOOST_PP_VARIADICS_SIZE
From: Edward Diener (eldiener_at_[hidden])
Date: 2018-08-19 20:24:24

On 8/19/2018 7:22 AM, Damien Buhl via Boost wrote:
> Dear Edward,
> 
> In comparison to BOOST_PP_SEQ, BOOST_PP_VARIADICS is limited to 64
> elements while BOOST_PP_SEQ is limited 255.
> 
> Is there a reason for the choice of 64 or could I patch
> BOOST_PP_VARIADICS to go as BOOST_PP_SEQ to a limit of 255 ?
> 
> Or asked differently do you think there  are in newer
> compilers/standards a way to have an unbounded BOOST_PP_VARIADICS
> implementation nowadays ?

BOOST_PP_TUPLE also has a 64 element limit.

I do not think there is a way to do an unbounded size, but if you have 
code to replace the BOOST_PP_VARIADIC_SIZE macro feel free to suggest it 
or create a PR.

There have been some other requests about increasing the limits of PP 
constructs as well as the numeric calculations whose limit is 256. These 
can always be manually done, but to what purpose, especially as the 
greater the limit the slower the preprocessor will run ? In your case is 
there really any practical point of having more than 64 possible 
variadic parameters ?

If there were techniques to have unbounded sizes for various limits PP 
would be glad to adopt them if they did not cause the preprocessor to 
slow down a great deal. But I do not know of such techniques.