DSLtest.md

if condition do
  # execute here when condition is true
end

while condtion do
  # execute here again and again while condition is true
end

origin

class NameList
  def initialize(name, &block)
    @name = name
    @list = []
  end
  
  def add(name, &block)
    @list << addition = NameList.new(name)
    addition
  end
  
  def print
    puts to_s
  end
  
  def to_s
    if @list.empty?
      "- " + @name.to_s
    else
      "[" + @name.to_s + "]\n" + @list.map(&:to_s).join("\n").gsub(/(^)/, "  ")
    end
  end
end

list = NameList.new(:Tsukukoma)

grade_2 = list.add(:grade_2)

class_1 = grade_2.add(:class_1)
class_1.add :Hideshima
class_1.add :Fujishiro

class_2 = grade_2.add(:class_2)
class_2.add :Hideshi
class_2.add :Fujishi

class_3 = grade_2.add(:class_3)
class_3.add :Hide
class_3.add :Fuji
class_3.add :Tsuku

list.print

instance_eval

class NameList
  def initialize(name, &block)
    @name = name
    @list = []
    
    instance_eval(&block) if block
  end
  
  def add(name, &block)
    @list << addition = NameList.new(name, &block)
    addition
  end
  
  def print
    puts to_s
  end
  
  def to_s
    if @list.empty?
      "- " + @name.to_s
    else
      "[" + @name.to_s + "]\n" + @list.map(&:to_s).join("\n").gsub(/(^)/, "  ")
    end
  end
end

list = NameList.new :Tsukukoma do
  add :grade_2 do
    
    add :class_1 do
      add :Hideshima
      add :Fujishiro
    end
    
    add :class_2 do
      add :Hideshi
      add :Fujishi
    end
    
    add :class_3 do
      add :Hide
      add :Fuji
      add :Tsuku
    end
  end
end

list.print

method_missing

class NameList
  def initialize(name, &block)
    @name = name.to_sym
    @list = []
    
    instance_eval(&block) if block
  end
  
  def add(name, &block)
    @list << addition = NameList.new(name, &block)
    addition
  end
  
  def print
    puts to_s
  end
  
  def method_missing(name, *args, &block)
    raise ArgumentError, "wrong number of arguments (" + args.size.to_s + " for 0)" unless args.empty?
    add(name, &block)
  end
  
  def to_s
    if @list.empty?
      "- " + @name.to_s
    else
      "[" + @name.to_s + "]\n" + @list.map(&:to_s).join("\n").gsub(/(^)/, "  ")
    end
  end
end

list = NameList.new :Tsukukoma do
  grade_2 {
    
    class_1 {
      hideshima
      fujishiro
    }
    
    class_2 {
      hideshi
      fujishi
    }
    
    class_3 {
      hide
      fuji
      tsuku
    }
  }
end

list.print

define_singleton_method

class NameList
  def initialize(name, &block)
    @name = name
    @list = []
    
    instance_eval(&block) if block
  end
  
  def add(name, &block)
    @list << addition = NameList.new(name, &block)
    
    define_singleton_method(name){ addition } unless respond_to?(name, true)
    
    addition
  end
  
  def print
    puts to_s
  end
  
  def to_s
    if @list.empty?
      "- " + @name.to_s
    else
      "[" + @name.to_s + "]\n" + @list.map(&:to_s).join("\n").gsub(/(^)/, "  ")
    end
  end
end

list = NameList.new :Tsukukoma do
  add :grade_2 do
    
    add :class_1 do
      add :Hideshima
      add :Fujishiro
    end
    
    add :class_2 do
      add :Hideshi
      add :Fujishi
    end
    
    add :class_3 do
      add :Hide
      add :Fuji
      add :Tsuku
    end
  end
end

list.print
list.grade_2.print
list.grade_2.class_1.print

delete

class NameList
  def initialize(name, &block)
    @name = name
    @list = []
    
    instance_eval(&block) if block
  end
  
  def add(name, &block)
    @list << addition = NameList.new(name, &block)
    addition
  end
  
  def print
    puts to_s
  end
  
  def to_s
    if @list.empty?
      "- " + @name.to_s
    else
      "[" + @name.to_s + "]\n" + @list.map(&:to_s).join("\n").gsub(/(^)/, "  ")
    end
  end
end

list = NameList.new :Tsukukoma do
  add :grade_2 do
    
    add :class_1 do
      add :Hideshima
      add :Fujishiro
    end
    
    add :class_2 do
      add :Hideshi
      add :Fujishi
    end
    
    add :class_3 do
      add :Hide
      add :Fuji
      add :Tsuku
    end
  end
end

list.print

list.instance_eval do
  @list.replace []
end
list.print