[boost] multi_array: num_dimensions() not a static member

Hi, Shouldn't num_dimensions() be a static member of multi_array as it only depends on the size_t template parameter? I am trying to write some template code that takes a type that models the multi_array interface however without an instance of this type I cannot determine the number of dimensions of the array. How should I do this or should a static method be added to the multi_array type? There is a line BOOST_STATIC_CONSTANT(std::size_t, dimensionality = NumDims); in the code but this is undocumented. John.