--- casecmp(other)   ruby 1.7 feature

    String#<=> [String/<=>] ƱͤʸνӤޤ
    ե٥åȤʸʸΰ㤤̵뤷ޤ

    Υ᥽åɤư $= ˤϱƶޤ

        p 'a' <=> 'A'      #=> 1
        p 'a'.casecmp('A') #=> 0

