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MathGroup Archive 2005

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Re: Threading 'Append'

  • To: mathgroup at smc.vnet.net
  • Subject: [mg62821] Re: Threading 'Append'
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 6 Dec 2005 00:03:17 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <dn226p$ksm$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

Mathematica evaluate an expression from the inner 
parts to the outer
parts. Since Append[{{1,2},{3,4},{5,6}},{a,b,c}] 
is evaluated to
{{1,2},{3,4},{5,6},{a,b,c}} the later evaluation 
of Thread[] does
not find a Append that it can thread ..

Thread[Hold[Append][{{1, 2}, {3, 4}, {5, 6}}, {a, 
b, c}]] // ReleaseHold

or
MapThread[Append, {{{1, 2}, {3, 4}, {5, 6}}, {a, 
b, c}}]

may help.

Regards

  Jens


"J Siehler" <jsiehler at gmail.com> schrieb im 
Newsbeitrag news:dn226p$ksm$1 at smc.vnet.net...
| If I run
|
| Thread[Append[{{1,2},{3,4},{5,6}},{a,b,c}]]
|
| I would expect to get
|
| {{1,2,a},{3,4,b},{5,6,c}}
|
| but in fact I get an 'Objects of unequal length' 
error.
|
| On the other hand,
|
| Thread[foo[{{1,2},{3,4},{5,6}},{a,b,c}]]
| %/.foo->Append
|
| gives what I wanted.  Can someone explain what's 
going on?
| 



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