MultiMap

ruby-talk
1 
(self[key] ||= []) << value

Now I wanna make an array of values unique.

So the code above becomes

unless ((self[key] ||= ).include? value )
self[key].push value
end

Is there a nicer way?

RR

2

Maybe just:

self[key] << value unless (self[key] ||= ).include? value

···

On Wednesday 04 December 2002 11:44 am, Roman Rytov wrote:

(self[key] ||= []) << value

Now I wanna make an array of values unique.

So the code above becomes

unless ((self[key] ||= ).include? value )
self[key].push value
end

Is there a nicer way?

RR

–
Bruce R. Williams :: [iusris/#ruby-lang] :: http://www.codedbliss.com

‘It does not require a majority to prevail, but rather an irate,
tireless minority keen to set brush fires in people’s minds.’
– Samuel Adams

3

PS:

You could also do:

((self[key] ||= []) << value).uniq!

… but that’s probably less efficient and arguably more ugly-- though shorter
(for educational purposes only)

···

On Wednesday 04 December 2002 05:15 pm, Bruce Williams wrote:

self[key] << value unless (self[key] ||= ).include? value

–
Bruce R. Williams :: [iusris/#ruby-lang] :: http://www.codedbliss.com

‘It does not require a majority to prevail, but rather an irate,
tireless minority keen to set brush fires in people’s minds.’
– Samuel Adams

4

What if you use Hash instead of Array as a value of self[key]? Then, as keys
are unique by definition, you could have something like:

(self[key] ||= Hash.new)[value] = true # or just nil

and later you reference it as

self[key].keys

Regards,
Gennady.

···

----- Original Message -----
From: “Bruce Williams” bruce@codedbliss.com
To: “ruby-talk ML” ruby-talk@ruby-lang.org
Sent: Wednesday, December 04, 2002 2:23 PM
Subject: Re: MultiMap

On Wednesday 04 December 2002 05:15 pm, Bruce Williams wrote:

self[key] << value unless (self[key] ||= ).include? value

PS:

You could also do:

((self[key] ||= ) << value).uniq!

… but that’s probably less efficient and arguably more ugly-- though
shorter
(for educational purposes only)

–
Bruce R. Williams :: [iusris/#ruby-lang] :: http://www.codedbliss.com

‘It does not require a majority to prevail, but rather an irate,
tireless minority keen to set brush fires in people’s minds.’
– Samuel Adams