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MathGroup Archive 2000

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Re: is there really no efficient way to delete an element from a list??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23983] Re: [mg23925] is there really no efficient way to delete an element from a list??
  • From: BobHanlon at aol.com
  • Date: Sun, 18 Jun 2000 03:01:05 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 6/16/2000 1:22:20 AM, b at hcii.de writes:

>hi, i tried to implement a queue with mathematica;
>is it possible that there is no O(1) way to get
>queue = Rest[queue]  ??
>
>it seems that mathematica uses call by value instead of call by reference
>here;
>i know that there are PrependTo[] and ApendTo[] for building the list;
>is there any equivalent to these functions to remove elements?
>
>or is there another way to implement a stack or queue with constant time
>access?

$Version

"4.0 for Power Macintosh (April 20, 1999)"

queue = Range[5]; 

Do[Print[queue]; queue = Rest[queue], {5}]

{1, 2, 3, 4, 5}
{2, 3, 4, 5}
{3, 4, 5}
{4, 5}
{5}

queue = Range[5]; 

Do[Print[queue]; queue = Drop[queue, 1], {5}]

{1, 2, 3, 4, 5}
{2, 3, 4, 5}
{3, 4, 5}
{4, 5}
{5}

queue = Range[5]; 

Do[Print[queue]; queue = Drop[queue, -1], {5}]

{1, 2, 3, 4, 5}
{1, 2, 3, 4}
{1, 2, 3}
{1, 2}
{1}


Bob Hanlon


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