ruby - Is there a bag implementation in Ruby?

Question

Is there an implementation of the bag collection (a collection like a set, that kept count of how many times an object is inserted)?

Answer 1

当然！它也称为multiset。这是一个很好的 ruby​​ 实现。

Answer 2

自己创建很简单，对吧？

class Bag
  def initialize
    @h = Hash.new{ 0 }
  end
  def <<(o)
    @h[o] += 1
  end
  def [](o)
    @h[o]
  end
end

bag = Bag.new
bag << :a
bag << :b
bag << :a
p bag[:a], bag[:b], bag[:c], bag
#=> 2
#=> 1
#=> 0
#=> #<Bag:0x100138890 @h={:b=>1, :a=>2}>