mpl::if_ or mpl::apply_if?

Hi! I am trying to migrate some parts of my code from loki to boost::mpl. Q1: which is the best way to perform nested if-then-else? Assume given "values": bool B1, bool B2; class ff, class tf, class ft, class tt; I replaced ----------------------------------------------------------- typedef typename Loki::Select::Result, typename Loki::Select::Result >::Result type; ----------------------------------------------------------- with typedef typename apply_if < bool_c<B1>, apply_if < bool_c<B2>, identity<tt>, identity<tf>

,

apply_if < bool_c<B2>, identity<ft>, identity<ff>

::type type;

Q2: Is apply_if always to be preferred over if_? Q3: (OT) Is there a mpl-equivalent to run-time case? best regards, Markus