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Re: Partitioning a list from an index

  • To: mathgroup at
  • Subject: [mg56953] Re: Partitioning a list from an index
  • From: bghiggins at
  • Date: Wed, 11 May 2005 05:24:08 -0400 (EDT)
  • References: <d5mv78$e05$>
  • Sender: owner-wri-mathgroup at

Guy, Here is one way to do the task:

partitionfunc[start_, size_, alist_] := alist /. {x1___,
    x_ /; x == start, y___} :> {x1, Apply[
    Sequence, Partition[Flatten[{x, Drop[{y}, -Mod[Length[{x, y}],
      size]], Apply[Sequence, Take[{y}, -Mod[Length[{x, y}], size]]]}



I am sure others will have a less kludgy way to do it.



Guy Israeli wrote:
> hello,
> how can partition a list (doesn't have to be with 'Partition') such
that the
> partition will begin with a specific index?
> like this:
> list1={1,2,3,4,5,6,7,8,9,10}
> and i might want to split it to pairs or threes from index 6 for
example, so
> for threes it will be
> {1,2,{3,4,5},{6,7,8},9,10}
> with or without padding to those that are left, depends on what it is

> possible, or maybe put them together or something
> for pairs it will be {1,{2,3},{4,5},{6,7},{8,9},10}
> again with or without padding
> thank you very much
> Guy

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