rs.cr

class Parameter
  property value
  def initialize(value, update)
    @value = value
    @update = update
  end
  def update
    @value = @update.call
  end
end

$system = {} of Symbol => Parameter

def get(param)
  $system[param].value
end

def update
  $system.each { |n, p| p.update }
end

def display
  $system.each { |n, p| puts "#{n} = #{p.value}" }
end

$system = {
  in: Parameter.new(3, ->{get(:in) + 1}),
  out: Parameter.new(5, ->{get(:out)}),
  mass: Parameter.new(100, ->{get(:mass) + get(:in) - get(:out)})
}

5.times do
  update
end
display