# File lib/parslet/atoms/can_flatten.rb, line 104
    def flatten_repetition(list, named)
      if list.any? { |e| e.instance_of?(Hash) }
        # If keyed subtrees are in the array, we'll want to discard all 
        # strings inbetween. To keep them, name them. 
        return list.select { |e| e.instance_of?(Hash) }
      end

      if list.any? { |e| e.instance_of?(Array) }
        # If any arrays are nested in this array, flatten all arrays to this
        # level. 
        return list.
          select { |e| e.instance_of?(Array) }.
          flatten(1)
      end

      # Consistent handling of empty lists, when we act on a named result        
      return [] if named && list.empty?

      # If there are only strings, concatenate them and return that. 
      foldl(list) { |s,e| s+e }
    end