From: Mathieu Bouchard <matju@...>
Date: 2000-12-03T08:54:24+09:00
Subject: [ruby-talk:6756] Re: Array Intersect (&) question

> |> >Use a hash.  Here's code to do both and more.  It assumes that
> |> >each element is unique in a given array:
> Using a hash makes it pretty fast, but it does not preserve the
> original order. 

Oh, I see.

> If no one requests order preservation, I will use
> hashes in &, |, and uniq.  What's your opinion?

I think you can preserve order and use hashes.

class Array
	def &(other)
		t = {}
		r = []
		other.each {|x| t[x]=1 }
		uniq.each  {|x| r<<x if t.has_key? x }
		r
	end
	def |(other)
		t = {}
		r = []
		(self+other).each {|x| r<<x unless t.has_key?(x); t[x]=1 }
		r
	end
	def uniq; self|[] end
end

matju