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MathGroup Archive 2005

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opposite of partition

  • To: mathgroup at
  • Subject: [mg57539] opposite of partition
  • From: Guy Israeli <guyi1 at>
  • Date: Tue, 31 May 2005 05:00:45 -0400 (EDT)
  • Sender: owner-wri-mathgroup at


How do I do the opposite of partition quickly?

for example:

l1= {{a, b, c, d, e}, {f, g, h, i, j}, {k, l, m, n, o}, {p, q, r, s, t}, {u, 
v, w,
x, y}}

and then if I partition it to blocks will result in

{{{{a, b}, {f, g}}, {{c, d}, {h, i}}}, {{{k, l}, {p, q}}, {{m, n}, {r, s}}}}

flattening it won't help, and its messy to do it by taking all first lines 
of the blocks, then second..

How can I do it quickly?



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