#include <boost/preprocessor/variadic/elem.hpp>
#define VAR_DATA a, b, c, d
BOOST_PP_VARIADIC_ELEM(0, VAR_DATA) // expands to a
BOOST_PP_VARIADIC_ELEM(3, VAR_DATA) // expands to d
根据 Boost 软件许可证,版本 1.0 分发。(请参阅随附文件 LICENSE_1_0.txt 或访问 www.boost.org/LICENSE_1_0.txt 复制)