From: Darshan Ishaya <darshan.ishaya@...>
Date: 2006-11-23T13:52:50+09:00
Subject: Re: Compare Array Values?

Ah, thanks.  I knew it would only work for classes with <=> defined, but 
I was naively assuming all important classes did.  (I've only been 
playing with Ruby for a couple of weeks.)  I didn't realize a class as 
important as Symbol didn't have it.

I could try a slightly better, but probably similarly flawed:

def same_elems?(array1, array2)
  return false unless array1.length == array2.length

  compare = Proc.new do |x,y|
    if (x.class == y.class)
      if x.respond_to?('<=>')
        x <=> y
      else
        x.to_s <=> y.to_s
      end
    else
      x.class.to_s <=> y.class.to_s
    end
  end

  return array1.sort(&compare) == array2.sort(&compare)
end

I'm now naively assuming all important classes implement to_s ; )

At least judging by this:

darshan@shadow ~ $ ri -T "<=>" | awk '{gsub(/<=>,/,"<=>\n");print}' | 
grep "<=>" | wc -l
25
darshan@shadow ~ $ ri -T "to_s" | awk '{gsub(/to_s,/,"to_s\n");print}' | 
grep "to_s$" | wc -l
116

it'll have a much better chance (almost 5 x) of working.  (Sorry, I 
haven't switched to Ruby one-liners yet; I'm sure I will soon.)

I guess it all depends on the application, and what classes are going to 
be in the arrays.  I sure had fun playing with it though.  I'm so stoked 
about Ruby.

Darshan

dblack@wobblini.net wrote:
> Hi --
>
> On Thu, 23 Nov 2006, Darshan.Ishaya wrote:
>
>> The Coolest Way:
>>
>> def same_elems?(array1, array2)
>>  return false unless array1.length == array2.length
>>
>>  compare = Proc.new do |x,y|
>>    if (x.class == y.class)
>
> You'd probably want to throw in a "and if x.respond_to?('<=>')".
>
>>      x <=> y
>>    else
>>      x.class.to_s <=> y.class.to_s
>
> The problem there is that it can't sort *within* a class that doesn't
> have <=> (and if it did, it would have sorted it that way :-)  So, for
> example:
>
>     p [:a,:b].sort(&compare)  # => [:a,:b]
>     p [:b,:a].sort(&compare)  # => [:b,:a]
>
>
> David
>