oop - ruby super keyword in initialize throws ArgumentError -

i'm learning ruby book based on ruby 1.9 i'm using 2.2

i have 2 classes (from book)

class point     def initialize(x,y)         @x,@y = x,y     end end  class point3d < point     def initialize(x,y,z)         super(x,y)         @z = z     end end 

however when call point3d.new(0,1,2) ruby interpreter raises argumenterror says wrong number of arguments (3 2).

why happening?

edit

i've omitted point class in required file.

i've tried call

require "./point.rb"  point = point.new(0,1) puts point 

which work expected

then added point3d class described on , tried call

require "./point.rb"  class point3d < point ... end  point1 = point3d.new(0,1,2) puts point1 

which raises argumenterror.

if put 2 classes in same file (point3d.rb) problem not happen, if put point3d class in point.rb error remains.

i understood problem was.

the book made example on how create initialize overload

class point     def initialize(x,y)         @x,@y = x,y     end      def self.new(x,y)         #other stuff         super     end end 

and missing super call point3d

i've commented self.new , point working expected.

it interesting note if add methods point in file point.rb this

class << point     def to_s         "foo"     end end 

point.rb works correctly.