I was thinking lately that it is a shame we can't do the following : boost::mpl::transform< SomeSequence, _1&> instead of the lengthy boost::mpl::transform< SomeSequence, add_reference<_1> > same goes for *, const, volatile : boost::mpl::transform< SomeSequence, volatile _1**&> Could it be possible to get such a behavior in MPL by having a pass of replacing type qualifier by corresponding metafunction until none are left then apply the lambda ? In the same vein, having a MPL trandform turning a sequence of std::vector into their corresponding value_type require out of line small metafunction to be written. I guess a macro like BOOST_MPL_ADAPTED_PLACEHOLDER( v, (type)(value_type)(reference)(const_reference) ) builds a whoel familly of _v1, ..., _v5 placeholder which behaves like _n and expose typedef called value_type etc ... that resolve to said small lambda function directly. This would allow for a terse: boost::mpl::transform< SomeSequence, _v1::reference> Are these ideas out of the question due to some internals of MPL I missed ? Are they worthy a patch ?