each_uniq.rb

module Enumerable
  def each_uniq(&block)
    return to_enum :each_uniq unless block_given?
    uniq_map = {}
    each do |*a|
      next if uniq_map.key?(a)
      uniq_map[a] = true
      block.call(*a)
    end
  end

  # @return [Enumerator]
  def each_uniq_by(&filter)
    Enumerator.new do |y|
      uniq_map = {}
      each do |*a|
        key = filter.call(*a)
        next if uniq_map.key?(key)
        uniq_map[key] = true
        y.yield(*a)
      end
    end
  end
end

src = [1, 1, 1, 1, 2, 2, 3, 4, 5, 6]
result = src.each_uniq.to_a

fail 'Dafuq happened there m8.' unless [1, 2, 3, 4, 5, 6] == result
result = src.each_uniq_by(&:even?).to_a

# actually I have no clue how to test this :x
fail 'each_uniq_by failed, epicly ;3' unless [1, 2] == result
result = src.each_uniq_by do |i|
  i * i
end.to_a
puts result.to_a