Untitled

Why can't I set the value for a multidimensional array?
class Solution

    def initialize
      @solution_matrix = [[[]]]
    end

    def [](receiver, provider, moment)
        return @solution_matrix[receiver][provider][moment]
    end

    def []=(receiver, provider, moment, value)
      puts "making " + receiver.to_s + " : " +  provider.to_s + " : " +moment.to_s + " -> " + value.to_s
      @solution_matrix[receiver][provider][moment] = value
    end

@solution[2,3,15]=false;

making 2 : 3 : 15 -> false

def list_disconnected
    number_of = 0
    for receiver in 0...@problem.number_of_receivers
      for provider in 0...@problem.number_of_providers
        for moment in 0...@problem.number_of_moments
          if (@solution[receiver,provider,moment]==false)
            puts receiver.to_s + " : " +  provider.to_s + " : " +moment.to_s
            number_of += 1
          end
        end
      end
    end
    puts number_of
  end

number of receivers: 40
number of providers: 6
number of moments: 50