The BOOST_PP_LIST_TO_TUPLE macro
      converts a list to a tuple. 
    Usage
     BOOST_PP_LIST_TO_TUPLE(list) 
    Arguments
    
      - list
-  The list to be converted. 
Remarks
     If 
list is, for example, (
a, (
b, (
c, 
BOOST_PP_NIL))),
      this macro will produce:
      
 (a, b, c) 
     Previously, this macro could not be used inside BOOST_PP_FOR. 
      There is no longer any such restriction.  It is more efficient,
      however, to use BOOST_PP_LIST_TO_TUPLE_R in such a situation.
      
      If the list to be converted is empty, as represented by 'BOOST_PP_NIL',
      the resulting tuple is undefined since a tuple cannot be
      empty.
    See Also
    
    Requirements
    
    Sample Code