The following two types are not used anywhere typedef typename ::boost::remove_cv::type rhs_nocv; typedef typename ::boost::remove_cv< typename ::boost::remove_reference< typename ::boost::remove_pointer::type >::type >::type rhs_noptr;
Shouldn't them be removed?
They are used, but not in the example of the doc. These shortcuts are used extensively in the macro FOBIDDEN_IF which determines if the operator is forbidden for fundamental types (to avoid compile time error). In the doc, I chose a simple case (unary_minus) where FORBIDDEN_IF is only ::boost::is_pointer< rhs_noref >::value Here is a more complex example (has_operator_plus.hpp): #define BOOST_TT_FORBIDDEN_IF\ ::boost::type_traits::ice_or<\ /* pointer with pointer */\ ::boost::type_traits::ice_and<\ ::boost::is_pointer< lhs_noref >::value,\ ::boost::is_pointer< rhs_noref >::value\ >::value,\ /* pointer with fundamental non integral */\ ::boost::type_traits::ice_and<\ ::boost::is_pointer< lhs_noref >::value,\ ::boost::is_fundamental< rhs_nocv >::value,\ ::boost::type_traits::ice_not< ::boost::is_integral< rhs_noref >::value >::value\ >::value,\ ::boost::type_traits::ice_and<\ ::boost::is_pointer< rhs_noref >::value,\ ::boost::is_fundamental< lhs_nocv >::value,\ ::boost::type_traits::ice_not< ::boost::is_integral< lhs_noref >::value >::value\ >::value,\ /* void* with fundamental */\ ::boost::type_traits::ice_and<\ ::boost::is_pointer< lhs_noref >::value,\ ::boost::is_void< lhs_noptr >::value,\ ::boost::is_fundamental< rhs_nocv >::value\ >::value,\ ::boost::type_traits::ice_and<\ ::boost::is_pointer< rhs_noref >::value,\ ::boost::is_void< rhs_noptr >::value,\ ::boost::is_fundamental< lhs_nocv >::value\ >::value\
::value
I have not see the utility of removing the reference typedef typename ::boost::remove_reference::type rhs_noref;
It is just used to know if the operation is forbidden for fundamental types and pointers. It avoids having everywhere typename ::boost::remove_reference< ... >::type. When checking for existence of operator, full type qualification is used (i.e. LHS or RHS). Frédéric