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MathGroup Archive 2005

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Re: Threading 'Append'

  • To: mathgroup at smc.vnet.net
  • Subject: [mg62834] Re: [mg62796] Threading 'Append'
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Tue, 6 Dec 2005 00:04:59 -0500 (EST)
  • References: <200512051840.NAA21108@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 6 Dec 2005, at 03:40, J Siehler wrote:

> 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?
>

All you need to do is:

In[9]:=
Thread[Unevaluated[Append[{{1, 2}, {3, 4}, {5, 6}},
     {a, b, c}]]]

Out[9]=
{{1, 2, a}, {3, 4, b}, {5, 6, c}}


The name of the function "Unevaluated" should make it self evident  
what happened here (I hope).

Andrzej Kozlowski


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