[Boost-users] [tuple][mpl][fusion] How to "prune" or "collapse" a tuple?

Hi all,

[added this line to make gmane happy.]

I'm looking for a way to remove "empty" values from a tuple. In other words, say I have a tuple T: tuple T; // where E can be either null_type, or mpl::void_, etc. I'd like for it to collapse into: tuple T2; Now, the reason I say "values" is because I found a way to do just that, but only for the types, which you'll find below. However, I can't figure out how to then *construct* the collapsed tuple given the original tuple (and its values.) Specifically, it's the `???' below that I'm missing. Thanks! // Collapse code: template <typename Sequence> struct tuple_from_sequence : mpl::reverse_fold < Sequence , tuples::null_type , tuples::cons > {}; template struct collapse > { typedef tuple original; typedef mpl::list sequence; typedef typename mpl::remove::type removed; typedef typename tuple_from_sequence<removed>::type type; static type construct(original const& t) { // return ???; } };