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Re: [xsl] How to Do Random "Shuffle"?


Subject: Re: [xsl] How to Do Random "Shuffle"?
From: "Wolfgang Laun wolfgang.laun@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 18 Sep 2014 11:13:58 -0000

random:random-sequence(N)

If this is supposed to produce a sequence of numbers in the range 1..N
while expecting it to contain every number of that range exactly once:
would this truly be a "random" sequence? I don't think so.

-W



On 18 September 2014 11:05, David Rudel fwqhgads@xxxxxxxxx <
xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> When I have to do this (essentially create a permutation of the numbers
> from 1 to N), I combine random:random-sequence with saxon:sort
>
> I'm away right now so I'm not working on a machine with XSLT, so the
> following syntax may be off, but I use:
>
> <xsl:variable name="rand" select="random:random-sequence(N)"/>
>
> <xsl:variable name="sorted.rand" select="saxon:sort($rand)"/>
>
> <xsl:variable name="permutation" select="$rand!index-of($sorted.rand,.)"/>
>
> The select attribute of the last can also be written as "for $i in $rand
> return index-of($sorted.rand,$i)"  .
>
>
> On Saturday, September 13, 2014, Eliot Kimber ekimber@xxxxxxxxxxxx <
> xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>> Using XSLT 2 I need to implement rendering of "match table" questions
>> where you have two sets of items, the match item and the thing it matches
>> to. I want to present this as a literal table, where the first column is
>> the match-from items in source order and the second column is the match-to
>> items, in random order.
>>
>> I think this is best characterized as a "shuffle" problem, where you want
>> to reorder a list randomly but all items in the list must be accounted
>> for.
>>
>> I can think of a recursive algorithm: given a list, generate a random
>> integer between 1 and the list length, select that item and add it to the
>> result list, then call this function on the original list minus the node
>> you just selected.
>>
>> Is there an easier or more efficient way to do it?
>>
>> Thanks,
>>
>> Eliot
>> ----------
>> Eliot Kimber, Owner
>> Contrext, LLC
>> http://contrext.com
>>
>>
>>
>
> --
>
> "A false conclusion, once arrived at and widely accepted is not dislodged
> easily, and the less it is understood, the more tenaciously it is held." -
> Cantor's Law of Preservation of Ignorance.
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