The BOOST_PP_LIMIT_VARIADIC
macro defines the maximum variadic data
size supported by the library.
Usage
BOOST_PP_LIMIT_VARIADIC
Remarks
This macro expands by default to 64. For a C++ standard
conforming preprocessor, the end-user can change this to 128 or
256 by defining this macro to either value before including any
library headers. This value can never be less than the value of BOOST_PP_LIMIT_TUPLE.