Re: [preprocessor] increase tuple size

From: Edward Diener (eldiener_at_[hidden])
Date: 2019-10-23 21:30:05

On 10/22/2019 4:41 PM, pavel b via Boost-users wrote:
> Hi,
> 
> preprocessor/config/limits.hpp limits tuple size to 64 elements. 
> Changing the BOOST_PP_LIMIT_TUPLE in this file seems not to have any 
> effect. Is it possible to increase the maximal tuple size?
> Are there scripts to update dependent macros like BOOST_PP_TUPLE_ELEM_* 
> in preprocessor/tuple/elem.hpp?
> 
> Thanks in advance

No, you should not be changing the limits and doing so will not actually 
change anything. If you want more than 64 tuple elements you could have 
a tuple whose elements themselves are tuples. For instance if you wanted 
256 tuple elements you could program this as a tuple with 64 elements 
and each of those elements is a tuple with 4 elements. Or if you like a 
tuple with 16 elements and each of those elements a tuple of 16 
elements. You get the idea.

My problem of changing this in Boost PP to some other greater hardcoded 
limit is that preprocessing speed will slow down overall if I do so, 
even for those people who do not need to use greater limits. If you feel 
there is some way of providing dynamic limits, where changing some limit 
value somehow changes the limit for all tuple functionality, please 
provide a PR for doing so, realizing that allowing dynamic changing of 
limits affects quite bit of tuple functionality in the Boost PP library 
which would have to have new implementations in your PR.