Ranking higher for higher number of matched criteria?

Hi all,

I am searching a field that I stored with something along these lines:

index << {:ngrams => ["-1/1/2/0", “1/0/-1/2”, “-2/6/5/1”]}

When I do a search for say something like:

FQL: ‘ngrams: “-1/1/2/0” “1/0/-1/2”’

I am getting the right results but the ranking seems to be off. My main
question is that if a document matches all terms (even if they are OR’d)
shouldn’t it have a higher ranking than one that has only one of them.
As far as I can tell this is not the case but I may be wrong.

I was wondering if there is a kind of “in set” operator in FQL that
effects the ranking of the document based on how many of the values in
the set are matched.

I would also like to ask about the special characters in Ferret queries
as per documentation:

:, (, ), [, ], {, }, !, +, ", ~, ^, -, |, <, >, =, *, ?, \

I can not find explanations for all of these characters, notably the {}
and [] brackets, ^ caret and ~ tilde. Can anyone point me to the place
that describes what each of these do. I am hoping something in there
will help me with my problem.

All the best,