Is hash ordered in JRuby 1.1?

Ruby JRuby
1

Hi all,

Do hashes maintain insertion order in JRuby 1.1? I would like to take a
JRuby hash to a Java LinkedHashMap and maintain insertion order
throughout.

Thanks,

Barbara

2

Hi there. It appears that it (JRuby 1.1.2) does maintain insertion
order, but that is different from MRI (1.8.6-p111).

$ jirb
irb(main):001:0> h={:a=>1,:b=>2}; h.delete(:a); h[:a]=3; h.keys
=> [:b, :a]

$ irb
irb(main):001:0> h={:a=>1,:b=>2}; h.delete(:a); h[:a]=3; h.keys
=> [:a, :b]

3

Hirotsugu A. wrote:

Hi there. It appears that it (JRuby 1.1.2) does maintain insertion
order, but that is different from MRI (1.8.6-p111).

$ jirb
irb(main):001:0> h={:a=>1,:b=>2}; h.delete(:a); h[:a]=3; h.keys
=> [:b, :a]

Note that 1.8.6 does not maintain insertion ordering in any way. JRuby
maintains exact insertion ordering, where deleted keys re-set will show
up later in the sequence.

  • Charlie

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4

However, Ruby 1.9 preserves hash ordering, so maybe this isn’t such a
bad thing.

Joshua

On 14-Jun-08, at 10:57 AM, Hirotsugu A. wrote:

JRuby maintains exact insertion ordering, where deleted keys re-set
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5

Joshua H. wrote:

However, Ruby 1.9 preserves hash ordering, so maybe this isn’t such a
bad thing.

On 14-Jun-08, at 10:57 AM, Hirotsugu A. wrote:

Right. And I think it is a bad idea to write code that relies on
JRuby’s (current) insertion-order-preserving behavior.

It’s probably not such a bad idea…it’s specified behavior now in Ruby
1.9 that insertion order is preserved for operations where it makes
sense (like keys, each, etc). It was specifically added.

  • Charlie

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6

On Jun 14, 2008, at 1:45 AM, Charles Oliver N. wrote:

  • Charlie

Right. And I think it is a bad idea to write code that relies on
JRuby’s (current) insertion-order-preserving behavior.

Hiro

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7

On Jun 14, 2008, at 1:17 PM, Charles Oliver N. wrote:

makes sense (like keys, each, etc). It was specifically added.

  • Charlie

Thank you both Joshua and Charlie for clarifying this.

Hiro

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8

Brilliant. Maintaining exact insertion order suits me perfectly.
Thanks!

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