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Re: newbie list question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115023] Re: newbie list question
  • From: image_doctor <matthew.prior at gmail.com>
  • Date: Tue, 28 Dec 2010 06:52:48 -0500 (EST)
  • References: <if70bt$330$1@smc.vnet.net>

On Dec 26, 9:02 am, Gareth Edwards <gareth.edwa... at cubicmotion.com>
wrote:
> Hi,
>
> Liking Mathematica a lot, but struggling with the early part of the learning curve, i.e. don't know what I don't know...
>
> What would be the neatest syntax for finding the first location of elements from one list in another? For example:
>
> listA = { 4,5,8,2,6,4 }
> listB = { 8,4,2 }
>
> I would like a function to return {3,1,4} in this case (the first location in A of each element in B)
>
> Many thanks!

You could try this ....

F[A_, B_] := Flatten@(First /@ (Position[A, #] & /@ B /. {} -> 0))


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