[boost] [variant] make_variant_over requirement

Hi, In the variant docs, in the make_variant_over section (Using a type sequence to specify bounded types), it is not clear what MPL sequence concept it is referring to. I was hoping it is a Forward Sequence, but I realized that when I try to use make_variant_over with a Forward Sequence, it fails trying to use mpl::clear, which hints that make_variant_over requires an MPL Extensible Sequence. This is rather undesirable. Is there a reason why this is so? Can't we lessen the requirement? The situation makes it not possible to use mpl views or fusion views for example. Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net