--- intern
--- to_sym ruby 1.7 feature

    ʸб륷ܥ(Symbol)֤ޤʥ륭饯
    ('\0')ޤʸ intern Ǥޤ(㳰 
    ArgumentError ȯޤ).

    ܥбʸˤ Symbol#to_s [Symbol/to_s]
    (ޤSymbol#id2name [Symbol/id2name])Ȥޤ

      p "foo".intern
      => :foo

      p "foo".intern.to_s == "foo"
      => true

