インタプリタ作ってみた

Rubyをやりだした理由は難解言語を作りたかったから（ぁ
というわけで、まずはHQ9+のインタプリタを書いてみた。

• • • • • • • • • • • • • -

hq9p.rb

class HQ9Plus

  def initialize(src)
    @src = src
    @count = 0
  end

  
  def run
    @src.each_char do |c|
      case c
      when "H"
        hello
      when "Q"
        print_source
      when "9"
        print_99_bottles_of_beer
      when "+"
        increment
      end
    end
  end
  
  

  private

  def hello
    puts "Hello, world!"
  end

  def print_source
    print @src
  end
  

  def print_99_bottles_of_beer
    99.downto(0) do |k|
      case k
      when 0
        before = "no more bottles"
        after = "99 bottles"
      when 1
        before = "1 bottle"
        after = "no more bottles"
      when 2
        before = "2 bottles"
        after = "1 bottle"
      else
        before = "#{k} bottles"
        after = "#{k-1} bottles"
      end

      if k == 0
        action = "Go to the store and buy some more"
      else
        action = "Take one down and pass it around"
      end

      puts "#{before.capitalize} of beer on the wall, #{before} of beer."
      puts "#{action}, #{after} of beer on the wall."
      puts "" unless k == 0
    end
  end

  def increment
    @count += 1
  end
end

HQ9Plus.new(ARGF.read).run

hello.hq

H

これをコンソールで叩いてみる。

うん、おもしろい。