newbie q: stripping duplicates

[pierodancona]

This is certainly well known, but not to me.

a = [{"aa"=>"bb"},{"aa"=>"bb"}]

=> [{"aa"=>"bb"}, {"aa"=>"bb"}]
=> [{"aa"=>"bb"}, {"aa"=>"bb"}]

Why? and, what should I use instead of .uniq
to remove the duplicate?

Thank you
Piero

 

[Stefano Crocco]

Alle Saturday 11 October 2008, (e-mail address removed) ha scritto:

This is certainly well known, but not to me.

a = [{"aa"=>"bb"},{"aa"=>"bb"}]

=> [{"aa"=>"bb"}, {"aa"=>"bb"}]

=> [{"aa"=>"bb"}, {"aa"=>"bb"}]

Why? and, what should I use instead of .uniq
to remove the duplicate?

Thank you
Piero

It works for me (with ruby-1.8.7-p72):

irb(main):005:0> a = [{"aa" => "bb"}, {"aa" => "bb"}]
=> [{"aa"=>"bb"}, {"aa"=>"bb"}]
irb(main):006:0> a.uniq
=> [{"aa"=>"bb"}]

Which version of ruby are you using?

Stefano

 

[Craig Demyanovich]

[Note: parts of this message were removed to make it a legal post.]

I get the same results as Piero on 1.8.6 p114, the most recent built-in
version on Mac OS X 10.5.5 (unless an update was included in the recent
security update that I haven't yet applied).

a = [{"aa"=>"bb"},{"aa"=>"bb"}] => [{"aa"=>"bb"}, {"aa"=>"bb"}]
a.uniq => [{"aa"=>"bb"}, {"aa"=>"bb"}]
exit

slapshot:~ cdemyanovich$ ruby -v
ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]

Craig

 

[pierodancona]

It works for me (with ruby-1.8.7-p72):

irb(main):005:0> a = [{"aa" => "bb"}, {"aa" => "bb"}]
=> [{"aa"=>"bb"}, {"aa"=>"bb"}]
irb(main):006:0> a.uniq
=> [{"aa"=>"bb"}]

Which version of ruby are you using?

Stefano

$ ruby --version
$ ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]

I guess I am out of luck?
In case, any 1.8.6 solution?
Piero

 

[Marcin Mielżyński]

(e-mail address removed) pisze:

This is certainly well known, but not to me.

a = [{"aa"=>"bb"},{"aa"=>"bb"}]

=> [{"aa"=>"bb"}, {"aa"=>"bb"}]
=> [{"aa"=>"bb"}, {"aa"=>"bb"}]

Why? and, what should I use instead of .uniq
to remove the duplicate?

1.8.7 and 1.9.x use deep hashing for hashes, to achieve that in 1.8.6
you need to monkey patch Hash: http://pastie.org/pastes/272194

lopex

 

[pierodancona]

you need to monkey patch Hash:http://pastie.org/pastes/272194

Monkeypatched. What a shame.

Thanks!
Piero

 

[Thomas B.]

1.8.7 and 1.9.x use deep hashing for hashes, to achieve that in 1.8.6
you need to monkey patch Hash: http://pastie.org/pastes/272194

So I believe this is sort of a bug in the old version? Because now I can
even get to this absurd:

irb(main):007:0> z={a[0]=>:x,a[1]=>:y}
=> {{"aa"=>"bb"}=>:x, {"aa"=>"bb"}=>:y} # absurd number 1
irb(main):008:0> z[{"aa"=>"bb"}]
=> nil # absurd number two

with the three {"aa"=>"bb"} object still reported to be ==.

TPR.

 

[Sebastian Hungerecker]

with the three {"aa"=>"bb"} object still reported to be ==.

Yes, but not eql?. In 1.8.6 there were no Hash#hash and Hash#eql? methods so
it used Object#hash and Object#eql?, which considers two objects equal only
when they're actually the same object.

HTH,
Sebastian

 

[Marcin Mielżyński]

Thomas B. pisze:

1.8.7 and 1.9.x use deep hashing for hashes, to achieve that in 1.8.6
you need to monkey patch Hash: http://pastie.org/pastes/272194

So I believe this is sort of a bug in the old version? Because now I can
even get to this absurd:

irb(main):007:0> z={a[0]=>:x,a[1]=>:y}
=> {{"aa"=>"bb"}=>:x, {"aa"=>"bb"}=>:y} # absurd number 1
irb(main):008:0> z[{"aa"=>"bb"}]
=> nil # absurd number two

with the three {"aa"=>"bb"} object still reported to be ==.

It's not an absurd, just a consequence Hash doesn't have it's own hash
(just default Object#hash). I agree it's a bit surprising but deep
hashing is slower by a fair amount.

Comparison function will not even be called here since it fails earlier,
at hash bucket lookup:

a = {"aa"=>"bb"}
b = {"aa"=>"bb"}
a.hash != b.hash

Btw, Hash doesn't use "==" for object comparison, it uses "eql?"

lopex