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)?

I am looking for something that is as standard as possible. I would prefer a core library to a gem and a gem to code that is not even a gem. — Guillaume Coté, Dec 20 '10 at 00:14

score 8 · Answer 1 · edited Jul 04 '14 at 09:19

8

Sure! It's also called a multiset. Here's a nice ruby implementation.

edited Jul 04 '14 at 09:19

mahemoff

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answered Dec 04 '10 at 03:41

Sam Ritchie

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The documentation talks about running a script as root. Is there a ubuntu package that include it? – Guillaume Coté Dec 04 '10 at 03:58
not that I'm aware of... looks like you'll have to get the source from that side and build it on your end. – Sam Ritchie Dec 04 '10 at 04:02
1

Is this so old that it pre-dates rubygems? – Andrew Grimm Dec 05 '10 at 12:33

score 6 · Answer 2 · answered Dec 04 '10 at 14:55

6

Pretty simple to create on your own, right?

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}>

answered Dec 04 '10 at 14:55

Phrogz

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Probably not as fast as one implemented in C. – Andrew Grimm Dec 05 '10 at 12:31
1

@AndrewGrimm Probably not noticeably slower given that this is a very lightweight shim on top of Hash, which is implemented in C. – Phrogz Dec 05 '10 at 14:33

Is there a bag implementation in Ruby?

2 Answers2

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