The BOOST_PP_SEQ_NIL macro is a placeholder macro for an empty seq.  
			It is only valid if it's elements are appended to the end of this empty 
			"seq." 
		
		
			Usage
		
		
			BOOST_PP_SEQ_NIL
		
		
			Remarks
		
		
			This macro is a utility macro intended as a empty starting point for appending 
			to the tail.  It is not a nil seq.  When an element is 
			appended to this macro, it expands on the element and to the element--thereby 
			removing itself.  For example, both BOOST_PP_SEQ_NIL(x) and BOOST_PP_SEQ_PUSH_BACK(BOOST_PP_SEQ_NIL,
			x) expand to x.
		
		
			If any BOOST_PP_SEQ_* macro (other than BOOST_PP_SEQ_PUSH_BACK) 
			is invoked with an argument that contains BOOST_PP_SEQ_NIL, the behavior 
			is undefined and in most cases will result in obscure errors.
		
		
			The closest thing available to BOOST_PP_SEQ_NIL for appending to the 
			head is BOOST_PP_EMPTY.  After all the elements have been 
			prepended, empty parenthesis can be invoked on the tail to remove the BOOST_PP_EMPTY.  
			As with BOOST_PP_SEQ_NIL, passing an argument that contains BOOST_PP_EMPTY
			to any BOOST_PP_SEQ_* macro (other than BOOST_PP_SEQ_PUSH_FRONT) 
			is undefined. 
		
		
			(It is also possible to start with an extra element and pop it off when you 
			have finished appending to it.)
		
		
			In C99, neither of these macros are necessary since it is legal to pass empty 
			arguments.
		
		
			See Also
		
		
		
			Requirements
		
		
		
			Sample Code