cartesian_product.jl

type Attr
    vals
    data
end

function cart_prod(sets...)
    result_size = length(sets)
    result_elems = reduce(*, 1, map(length, sets))
    result = zeros(result_elems, result_size)
    scale_factor = result_elems
    for j = 1:result_size
        set = sets[j]
        set_elems = length(set)
        scale_factor = div(scale_factor, set_elems)
        for i = 1:result_elems
            pos = div(i, scale_factor) % set_elems + 1 |> int
            result[i, j] = set[pos]
        end
    end
    return result
end

function cart_prod(attrs::Attr...)
    vals_list = [a.vals for a = attrs]
    return cart_prod(vals_list...)
end