This macro is intended to avoid the use of 
automatic-recursion at deep expansion depths. 
			
Automatic-recursion at such depths can be inefficient on some preprocessors. 
			It is not intended to be used directly with the invocation of macros with a 
_R suffix such as:
			
				BOOST_PP_LIST_ENUM_R(BOOST_PP_DEDUCE_R(), (a, (b, (c, BOOST_PP_NIL))))
			
			If it is used in this context, the 
_R macro will fail. 
			The 
_R macros directly concatenate to the 
r parameter that is passed to them,
			which would prevent 
BOOST_PP_DEDUCE_R() from expanding. 
			Furthermore, it is pointless to use this macro in a situation such as this
			because it would already be too late to gain any efficiency.