Implementing Set Functionality (equality) in Ruby Classes

point_example.rb

require 'set'

# Here's our simple point class that contains two integers, x and y
class Point
  attr_accessor :x, :y

  def initialize(x,y)
    @x, @y = x, y
  end

  def eql?(other)
    other.is_a?(Point) &&
    [x,y] == [other.x, other.y]
  end

  def hash
    [x,y].hash
  end
end

p1 = Point.new(1,1)
p2 = Point.new(1,1)
p3 = Point.new(0,1)

puts p1 == p2                # false
puts p1.eql?(p2)             # true
points = [p1, p2, p3]        
points.each {|e|
  p e.hash                   # 13, 13, 9
}

# NOTE: your memory locations will vary
puts Set.new(points).inspect # #<Set: {#<Point:0x103573880 @x=1, @y=1>, #<Point:0x1035735b0 @x=0, @y=1>}> 
puts points.uniq.inspect     # [#<Point:0x103573880 @x=1, @y=1>, #<Point:0x1035735b0 @x=0, @y=1>]