From: Joel VanderWerf <vjoel@...>
Date: 2009-07-28T04:02:38+09:00
Subject: Re: Set class and repetetive elements

Marcin G坦rski wrote:
> Hi,
> I would like to know if there is possibility to add values like but have
> a few elemens with the same value:
> 
> irb(main):002:0> require 'set'
> => true
> irb(main):003:0> a = Set.new
> => #<Set: {}>
> irb(main):004:0> a.add(1)
> => #<Set: {1}>
> irb(main):005:0> a.add(1)
> => #<Set: {1}>
> irb(main):006:0> a.add(1)
> => #<Set: {1}>
> irb(main):007:0> a.add(2)
> => #<Set: {1, 2}>
> irb(main):008:0> a.add(3)
> => #<Set: {1, 2, 3}>
> irb(main):009:0> a.add(4)
> => #<Set: {1, 2, 3, 4}>
> irb(main):010:0> a.add(5)
> => #<Set: {5, 1, 2, 3, 4}>
> irb(main):011:0> a.add(6)
> => #<Set: {5, 6, 1, 2, 3, 4}>
> irb(main):012:0> a.add(1)
> => #<Set: {5, 6, 1, 2, 3, 4}>
> 
> It would be nice to have for example {5, 1, 1, 1} in Set class object.
> Is it possible? Which method should I use to add element in that way?

You can build something based on hashes (Set is itself based on Hash):

class Bag
   def initialize
     @h = {}
   end
   def add val
     (@h[val] ||= []) << val
   end
   def [](key)
     @h[key]
   end
   def inspect
     "#<Bag: #{@h.values.inspect}>"
   end
end

bag = Bag.new

bag.add 1
bag.add 1
bag.add 1

bag.add 2
bag.add 2

bag.add 3

p bag # ==> #<Bag: [[1, 1, 1], [2, 2], [3]]>

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407