Re: [Boost-users] [mpl] Constant time mpl::contains<mpl::set>

strasser@uni-bremen.de wrote:

Hi,

I'd like to be able to query if a MPL Sequence contains a certain type, aka mpl::contains. But mpl::contains is documented to always have linear complexity, even for mpl::set's. How can you differentiate between types of MPL Sequences, so you can use mpl::at for sets and mpl::contains for vectors? MPL itself seems to do this by template specialization, e.g. for mpl::at, which is overloaded. But template specialization relies on MPL implementation details, is there a way to detect any type that models an associative sequence? I can't find something like mpl::is_set nor a tag to dispatch with in the AssociativeSequence concept.

Thank you,

Stefan

I, myself, use : http://www.boost.org/doc/libs/1_41_0/libs/mpl/doc/refmanual/sequence-tag.htm... and I check if the returned type is one of the defined tag. HJere for mpl::set, you can do is_same > > so you don't rely on the explicit type of the tag itself.