1-documentation.md

Ruby docs for Array#uniq

From the docs:

uniq → new_ary uniq { |item| ... } → new_ary Returns a new array by removing duplicate values in self.

If a block is given, it will use the return value of the block for comparison. It compares values using their hash and eql? methods for efficiency. self is traversed in order, and the first occurrence is kept.

2-uniq.rb

class Uniq
  attr_reader :item

  def initialize(item)
    @item = item
  end
end

class Eql < Uniq
  def eql?(other)
    self == other
  end
end

puts "Only `eql?` defined:"
puts "Running: [Eql.new(1), Eql.new(1)].uniq"
p [Eql.new(1), Eql.new(1)].uniq
puts

class Hsh < Uniq
  def hash
    item.hash
  end
end

puts "Only `hash` defined:"
puts "Running: [Hsh.new(1), Hsh.new(1)].uniq"
p [Hsh.new(1), Hsh.new(1)].uniq
puts

class EqlAndHash < Uniq
  def eql?(other)
    other.item == self.item
  end

  def hash
    item.hash
  end
end

puts "Both `hash` and `eql?` defined"
puts "Running: [EqlAndHash.new(1), EqlAndHash.new(1)].uniq"
p [EqlAndHash.new(1), EqlAndHash.new(1)].uniq
puts

class DoubleEqualsAndHash < Uniq
  def ==(other)
    other.item == self.item
  end

  def hash
    item.hash
  end
end

puts "Both `hash` and `==` defined"
puts "Running: [DoubleEqualsAndHash.new(1), DoubleEqualsAndHash.new(1)].uniq"
p [DoubleEqualsAndHash.new(1), DoubleEqualsAndHash.new(1)].uniq

3-output.txt

Only `eql?` defined:
Running: [Eql.new(1), Eql.new(1)].uniq
[#<Eql:0x007facd400ed48 @item=1>, #<Eql:0x007facd400ed20 @item=1>]

Only `hash` defined:
Running: [Hsh.new(1), Hsh.new(1)].uniq
[#<Hsh:0x007facd400e938 @item=1>, #<Hsh:0x007facd400e910 @item=1>]

Both `hash` and `eql?` defined
Running: [EqlAndHash.new(1), EqlAndHash.new(1)].uniq
[#<EqlAndHash:0x007facd400e5a0 @item=1>]

Both `hash` and `==` defined
Running: [DoubleEqualsAndHash.new(1), DoubleEqualsAndHash.new(1)].uniq
[#<DoubleEqualsAndHash:0x007facd400e2a8 @item=1>, #<DoubleEqualsAndHash:0x007facd400e258 @item=1>]