class Array

   def subar_indices(ar=[], temp=[])
      temp = temp.dup
      self.each_with_index { |item, index| 
         if item.class == Array
            temp << index
            ar << temp
            ar = item.subar_indices(ar, temp)
         end
      }
      ar.uniq
   end


   def extract_subar_indices
      subarray_indices = self.subar_indices  # subarray_indices is a two-dimensional array
      # puts subarray_indices.inspect
      
      return subarray_indices if subarray_indices.empty?

      first_subar = subarray_indices.shift   # the first subarray contains all two-dimensional subarray indices                

      subarray_indices.each do |subar|
         subar_size = subar.size
         str = ""
         count = -1
         (subar_size - 1).times { count += 1; str << ".fetch(subar[#{count}], [])" }
         str << ".fetch(subar[#{count + 1}], {}"
         str = "self" << str
         if eval(str).class == Hash then subar.shift; redo end
      end

      first_subar.reverse.each do |item| subarray_indices.unshift([item]) end
      subarray_indices
   end

end


array = [1, 2, [3, 4, [5, 6]], 7, 8, [9]]

indices = array.extract_subar_indices

puts indices.inspect  # [[2], [5], [2, 2]]

class Hash

   def extract_keys

      keys = []

      each_pair do |k1, v1|

         if v1.is_a?(Hash)

            v1.each_pair { |k2, v2|
               if !v2.is_a?(Hash) then keys << [k1, k2]; next end
            v2.each_pair { |k3, v3|
               if !v3.is_a?(Hash) then keys << [k1, k2, k3]; next end
            v3.each_pair { |k4, v4|
               if !v4.is_a?(Hash) then keys << [k1, k2, k3, k4]; next end
            v4.each_pair { |k5, v5|
               if !v5.is_a?(Hash) then keys << [k1, k2, k3, k4, k5]; next end
            v5.each_pair { |k6, v6|
               if !v6.is_a?(Hash) then keys << [k1, k2, k3, k4, k5, k6]; next end
               # add more v[n].each_pair ... loops to process more hash dimensions
            } } } } }      # "}" * 5

         else
            keys << [k1]
         end

      end
      
      keys

   end


   def all_values
      extract_keys.map do |subar|
         key = ""
         subar.size.times { |i| key << "[subar[#{i}]]" }
         hash_str = "self" << key << " rescue nil"   # example: "self[subar[0]][subar[1]][subar[2]][subar[3]] rescue nil"
         hash_value = eval(hash_str) 
      end
   end


#-------------------------


   # Find every path and it's value in a Hash, http://snippets.dzone.com/posts/show/3565
   # Author: Florian Aßmann

   def each_path
      raise ArgumentError unless block_given?
      self.class.each_path(self) { |path, object| yield(path, object) }
   end

   protected
   #def self.each_path(object, path = '', &block)
   def self.each_path(object, path = [], &block)   # alternative
      if object.is_a?(Hash)
         object.each do |key, value|
            #self.each_path(value, "#{ path }#{ key }/", &block)
            self.each_path(value, [path , key].flatten, &block)   # alternative
         end
      else 
         yield(path, object)
      end
   end 

end


h = {"a"=>"b", "c"=>"d", 1=>{2=>{"e"=>"f", 3=>{4=>"value"}}}} 

puts h[1][2].class          # Hash
puts h[1][2]["e"].class     # String

extracted_keys = h.extract_keys
puts extracted_keys.inspect         # [["a"], [1, 2, "e"], [1, 2, 3, 4], ["c"]]

puts h[1][2].has_key?("e")                 # true
puts extracted_keys.include?([1, 2, "e"])  # true


h = {700=>{4=>"value"}, "a"=>"b", 3=>{4=>"value"}, "c"=>"d", 1=>{2=>{"e"=>"f", 3=>{4=>"value"}, 300=>{4=>"value"}}}} 
p h
p h.extract_keys    #=> [["a"], [1, 2, "e"], [1, 2, 300, 4], [1, 2, 3, 4], ["c"], [700, 4], [3, 4]]
p h.all_values      #=> ["b", "f", "value", "value", "d", "value", "value"]


#-----------------


paths = []
complex_hash = Hash[
  :a => { :aa => '1', :ab => '2' },
  :b => { :ba => '3', :bb => '4' }
]
complex_hash.each_path { |path, value| paths << [ path, value ] }

p paths    # => [[[:b, :ba], "3"], [[:b, :bb], "4"], [[:a, :ab], "2"], [[:a, :aa], "1"]]
puts


h = {"a"=>"b", "c"=>"d", 1=>{2=>{"e"=>"f", 3=>{4=>"value"}}}} 
h = {"a"=>"b", "l" => lambda { |x| x+1 }, 1=>{2=>{"e"=>"f", 3=>{4=>"value"}}}} 
h = {700=>{4=>"value"}, "a"=>"b", nil => "NILVALUE", 3=>{4=>"value"}, "c"=>"d", 1=>{2=>{"e"=>"f", 3=>{4=>"value"}, 300=>{4=>"value"}}}} 

p h
p h.extract_keys

keys = []
h.each_path { |path, value| keys << path }
p keys   # complete key sequences (with last key not pointing to another hash)

paths = []
h.each_path { |path, value| paths << [ path, value ] }
p paths   # complete key sequences plus values

vals = []
h.each_path { |path, value| vals << value }
p vals   # all values of complete key sequences

p h.all_values   # same

class Hash
  def mdh(*mkeys)
     value = mkeys.pop
     count = 0
     mdhash = lambda { |*keys|
                   count += 1
                   keys_clone = keys.clone if count == 1 # keys_clone will return nil for count > 1 in Hash.new
                   Hash.new(var = keys_clone || keys.shift).update(var => mdhash[*keys] || value) unless keys.empty? 
                 }
     mdhash.call(*mkeys)
  end
end

h = Hash.new.mdh(1, 2, 3, 4, "value")

puts h.inspect  # {[1, 2, 3, 4]=>{1=>{2=>{3=>{4=>"value"}}}}}

k = [1, 2, 3, 4]
puts h.has_key?(k)
puts h[k][k[0]][k[1]][k[2]][k[3]]  # value


     

class Array

   def mda(*mds)

      count = -1

      mdarray = lambda { |*ds| 
        Array.new( ds.shift || 0 ).collect {
            x = mdarray[*ds] unless ds.empty?
            if x == nil then count += 1; x = self.at(count); end
            x
            }
      }

      mdarray.call(*mds)    

   end

end


ar1 = (1..24).to_a    # input data

ar2 = ar1.mda(1, 2, 3, 4)   # note: 1 x 2 x 3 x 4 = 24 
puts ar2.inspect

puts ar2[0..0][0..1][0..2][0..3].inspect    # returns entire ar2
puts ar2[0][1][2][0..3].inspect             # returns last subarray 
            

# extracting subarrays
ar = []
ar2.each { |a| a.each { |b| b.each { |c| ar << c if c.last > 6 } } }
puts ar.inspect


# extracting only the first subarray that meets the if-condition
ar = []
ar << catch(:val) { ar2.each { |a| a.each { |b| b.each { |c| throw(:val, c) if c.last > 6 }}} }
puts ar.inspect