ruby 二つの枚举を外部イテレーターの机能で突き合わせを行いマージする

Posted 2021-05-16

class Merger
  def initialize(master, tran)
    @master = master
    @tran = tran
  end

  def match(master, tran)
    puts " match: #{master}, #{tran}"
  end

  def master_only(value)
    puts "m only: #{value}"
  end

  def tran_only(value)
    puts "t only: #{value}"
  end

  def matching()
    master_value = enum_next(@master)
    tran_value = enum_next(@tran)

    while (master_value || tran_value)
      case cmp(master_value, tran_value)
      when 0
        match(master_value, tran_value)
        master_value = enum_next(@master)
        tran_value = enum_next(@tran)
      when -1
        master_only(master_value)
        master_value = enum_next(@master)
      else
        tran_only(tran_value)
        tran_value = enum_next(@tran)
      end
    end
  end

  private

  def enum_next(enum)
    begin
      enum.next
    rescue StopIteration
      false
    end
  end

  def cmp(master, tran)
    return  1 unless master
    return -1 unless tran
    master <=> tran
  end
end

a = [1,3,4,8,6].sort.to_enum
b = [2,3,5,6,7].sort.to_enum

match = Merger.new(a, b)
match.matching()

# m only: 1
# t only: 2
#  match: 3, 3
# m only: 4
# t only: 5
#  match: 6, 6
# t only: 7
# m only: 8