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Minor feature request: BOOST_PP_IGNORE or update docs for BOOST_PP_EMPTY

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
45/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
cpp
Domain
compilers

Research direction

Start with the BOOST_PP_EMPTY reference documentation and compare its limitations with boost/vmd/empty.hpp, where BOOST_VMD_EMPTY(...) is mentioned as an existing alternative. Read #34 for the context behind the signature constraint. Done means either documenting the alternative in the BOOST_PP_EMPTY reference or adding the requested BOOST_PP_IGNORE(...) behavior, with the chosen approach clearly covered.

Written by the indexing model from the issue text.

Description

The current BOOST_PP_EMPTY() is not variadic, so its usefulness in BOOST_PP_IF() and the like is limited to when there are no arguments/params in the resultant call.

For example, this doesn't work:

#define X(a, b) result(a, b)
#define MACRO(a, b, c) BOOST_PP_IF(c, X, BOOST_PP_EMPTY)(a, b)

As explained in #34, changing the signature of BOOST_PP_EMPTY() is impractical, and another solution exists: BOOST_VMD_EMPTY(...) in boost/vmd/empty.hpp.

So this is a very minor issue, but it would be nice if either:

  1. There were a BOOST_PP_IGNORE(...) to do this, or...
  2. The reference docs for the BOOST_PP_EMPTY could also point to the VMD macro to use instead.
Dominant language
C++
Stars
118
Forks
76
PR merge metrics
No merged PRs in 30d

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