From: Daniel N <has.sox@...>
Date: 2006-11-23T12:16:37+09:00
Subject: Re: Compare Array Values?

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On 11/23/06, Gabriele Marrone <gabriele.marrone@gmail.com> wrote:
>
>
> On 23/nov/06, at 02:04, Daniel N wrote:
>
> > I want to check to see if two arrays contain the same values.
> > That is, are they the same array but not in the same order.
>
>    def are_these_arrays_equal?(a1, a2)
>      return false if a1.size != a2.size
>      a2 = a2.dup # a2 will be modified, so let's duplicate it
>      for i1 in a1
>        return false unless a2.include? i1
>        # need to delete just the *first* occurrence of i1 in a2
>        # (Array#delete deletes them all)
>        found = false
>        a2.delete_if {|i2| found = !found && i1 == i2 }
>      end
>      # a2 is now empty, since its size was equal to a1 size
>      return true
>    end
>
> This should work with multiple occurrences of the same object,
> different objects (so different object_id) that seem to be equal (by
> comparing them with ==), nil values (#find() is a bit tricky),
> objects that do not respond to <=>.
> Did I miss any case?


I've made a list of the cases so far that I can think of, in a response to
Davids post.  The elements could be of arbitrary type.

Anyway I think it's a bit slow (delete_if goes on even if we deleted
> the only one we wanted to, moreover it duplicates a whole array), but
> who cares? We're using ruby, we probably aren't looking for speed
> anyway :P


The case that I want to use it for is as a test helper so speed is not
critical.  I want to make sure that I don't have duplicate attributes in an
association in rails that is not a straight forward use of
validates_uniquness_of

Thanx for your help... I'll give this one a go when I get to my computer.

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