...one of the most highly
regarded and expertly designed C++ library projects in the
world. — Herb Sutter and Andrei
Nearly all macros in VMD have equivalent reentrant versions which are meant to be used in a BOOST_PP_WHILE loop. These are versions which have an underscore D suffix, take the next available BOOST_PP_WHILE iteration as their first parameter, and then have the exact same functionality as their unsuffixed equivalents. They can be used in BOOST_PP_WHILE loops to provide slightly quicker preprocessing but, as the documentation for BOOST_PP_WHILE and BOOST_PP_WHILE_##d explain, they do not have to be used.
These macros are: