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MathGroup Archive 2005

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Re: pattern matching all list elements but last

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54580] Re: [mg54539] pattern matching all list elements but last
  • From: János <janos.lobb at yale.edu>
  • Date: Wed, 23 Feb 2005 03:12:00 -0500 (EST)
  • References: <200502220924.EAA10849@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Well, I still did not conquer rules.  here is with Map and If:

In[15]:=
Table[(If[IntegerQ[#1] &&
       #1 =!= Last[ls[[i]]],
      #1 + 100, #1] & ) /@
    ls[[i]], {i, 1,
    Length[ls]}]
Out[15]=
{{1}, {102, 3}, {104, 105,
    6}, {107, 108, 109, 10}}


On Feb 22, 2005, at 4:24 AM, Trevor Baca wrote:

> hi mathgroup folks,
> let's say ls looks like this:
>   ls = {{1}, {2,3}, {4,5,6}, {7,8,9,10}}
> is there an elegant way to match all integers *except the last
> (rightmost)* in each list and, say, add 100 to each?
>   ls /. <magic replacement rule goes here>
> or
>   ls //. <magic replacement rule goes here>
> to give {{1}, {102,3}, {104,105,6}, {107,108,109,10}}?
> this works:
>   Release[ ls //. {a___, b_Integer, c___, z_Integer} :> {a, Hold[b +
> 100], c, z} ]
> but is there a more elegant pattern, possibly one that avoids the
> Hold-Release trick?
> trevor.


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