From: Chad Perrin <perrin@...>
Date: 2008-10-30T11:22:55+09:00
Subject: array comparison

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I can easily write a program to compare the contents of arrays, of
course.  Ruby's great that way.  In a matter of a minute or so, I could
write a program that compares small numbers of items in a list with small
numbers of items in another list and give me output that consists of
things that appear in both, or those that don't appear in both, or those
that appear in one and not the other.

I find myself contemplating doing much the same thing, but with lists
that contain millions of entries.  I tend to guess that loading each list
into an array and running a direct comparison of them:

  array_1 =3D [millions of things]
  array_2 =3D [millions of things]
  array_3 =3D array1 & array2

=2E . . would fill up RAM in a hurry and drag system performance on a
typical desktop computer to a standstill.  What sort of approach would
the expert Ruby hackers suggest for achieving much the same ends without
taking all week and risking a stack overflow?

--=20
Chad Perrin [ content licensed PDL: http://pdl.apotheon.org ]
Colin McFadyen: "Unix is not an 'a-ha' experience, it is more of a
'holy-shit' experience."

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