How to use nested arrays in ActionWebService?

Hi list.

I am writing a data structure definition for my web service API that
has - besides others - a nested array of integers: I want to have an
array that contains arrays which themselves contain two integer values.

An example for this is:

[ [1, 2], [2, 400] ]

These values represent a distribution and in this exapmmle this means
that the event “hit 1 time” occured two times and “hit 2 times”
occured 400 times.

When I try to implement this the following way I get an error (“nil
where it was not expected, maybe you wanted an array instead”):

class ProductStatistics < ActionWebService::Struct
member :name, :string

member :hit_distribution, [[:int]]
end

When I changed this to a flat integer array, it worked:

class ProductStatistics < ActionWebService::Struct
member :name, :string

member :hit_distribution, [:int]
end

Now, my question: Is it possible to specify that I want nested arrays
of integers in my web service API and if yes: how?

Regards,

Manuel H.