Alexander Nasonov <alnsn@yandex.ru> writes:
Jonathan Turkanis wrote:
"Tobias Schwinger" <tschwinger@neoscientists.org> wrote in message
However, I guess you are talking about another as_sequence distinct from mpl::as_sequence...
Yes, I misunderstood the question. I don't like the idea of 'overloading' mpl::as_sequence this way, but generating sequences from function types vice versa seems like a legitimate request. I'm still not sure I see the difficulty though.
Yes, I mean mpl::as_sequence. I know, overloading it this way is not a best idea but, I can think of mpl::as_sequence only as a sugar. That is, if template X accepts MPL sequence, you can pass an ordinary type if X has mpl::as_sequence underneath:
X<mpl::vector<int> > // 1 X<int> // 2 - sugar for 1
Sequence concept is mixed up with ordinary types but if you tell a user about it, they can accept it. If mpl::as_sequence treated function types as I suggest, it could introduce more sugar:
X<int(char)> // 3 - sugar for mpl::vector<int,char>
but this could confuse a user.
FWIW, we didn't cover as_sequence in the book because we really couldn't come up with a use case that justified the non-uniformity in generic programs. If the type you pass happens to be a sequence already it gets treated differently :(. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com