"Delfin Rojas"
What I'm trying to do is make a variant that is a superset of another variant. For that, I make an initial mpl sequence with the types of the first variant and create it. Then I make a second list with the extra types of the second variant. I would then like to create the second variant passing the joint list of the first types sequence and second types sequence. That is why I wanted to use joint_view. Then I thought I would just push_back each of the second variant types to the first types sequence but that failed too. Finally I am doing an insert at the end (essentially a push_back but not quite).
If you just need to concatenate two sequences, you can use fold_backward and
push_front, something like:
template
{};
HTH, Arkadiy