r_chunk.rb

# Chunk is going to introduce the concept of passing "state" through reduce
def r_chunk
  data = reduce({
    result: [],
    stack:  []
  }) { |state, item|
    new_value = yield(item)

    if state[:stack].empty?
      stack = [new_value, [item]]
    else
      previous_value, collection = state[:stack]

      if new_value == previous_value
        stack = [new_value, [*collection, item]]
      else
        result = [*state[:result], state[:stack]]
        stack  = [new_value, [item]]
      end
    end

    {result: result, stack: stack}
  }

  [*data[:result], data[:stack]]
end