Bested by Blakeley yet again!
For the sake of posterity...
---
declare function local:shuffle($seq as item()*)
{
for $i in local:randIntSeq(fn:count($seq))
return $seq[$i]
};
let $seq := ('apple', 'banana', 'cherry', 'danish', 'egg')
return local:shuffle($seq)
---
Thanks Mike, not sure I'll ever stop learning from you,
Eric
Michael Blakeley wrote:
Here's a shuffle function that will sort randomly, but repeatably (ie,
based on a seed). This is quick with a small use-case, but the longer
the list, the longer this will take to run. Query results may contain
millions of items, so it might take a while to re-sort them. But you
could reasonably call cts:uris() with a cts:query argument, then re-sort
the first N uris randomly.
declare variable $LIST as xs:string+ := (
for $i in 1 to 26
return codepoints-to-string(96 + $i)
);
declare function local:shuffle($list as xs:string*, $seed as xs:integer?)
as xs:string*
{
if (empty($list)) then $list
else
let $seed :=
if ($seed) then $seed else xdmp:random()
for $i at $x in $list
order by xdmp:hash64(string(64 * $x + xs:double($seed) * 256))
return $i
};
(: test :)
text { local:shuffle($LIST, 17) },
text { local:shuffle($LIST, 17) },
text { local:shuffle($LIST, 18) },
text { local:shuffle($LIST, ()) }
-- Mike
On 2009-06-26 14:33, Eric Palmitesta wrote:
This seems to work for me, though I'm not sure if it will apply
effectively to your situation.
---
xquery version "1.0-ml";
declare function local:randIntSeq(
$in as xs:integer*, $out as xs:integer*)
{
if (count($in) eq 0) then $out
else
let $r := xdmp:random(count($in))
return local:randIntSeq(
($in[1 to ($r - 1)], $in[($r + 1) to last()]),
($out, $in[$r])
)
};
declare function local:randIntSeq($max as xs:integer)
{
local:randIntSeq((1 to $max), ())
};
let $seq := ('apple', 'banana', 'cherry', 'danish', 'egg')
let $seqLength := fn:count($seq)
return
for $i in local:randIntSeq($seqLength)
return $seq[$i]
---
It just generates a sequence of random integers which you can use to
pull items out of your desired sequence.
Eric
Mindie Sorenson wrote:
Does anyone have any good ideas on how to return query results in a
random order?
Thanks
Mindie
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