How is satisfies different from where ?

[Michael Kay]

The "some" and "every" expressions can always be rewritten in terms of
exists() or empty() applied to a corresponding FLWOR expression. They may
provide greater expressive clarity and may perform better in some
implementations, but they are functionally redundant.

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay 

> -----Original Message-----
> From: http://x-query.com/mailman/listinfo/talk 
> [mailto:http://x-query.com/mailman/listinfo/talk] On Behalf Of David
> Sent: 22 May 2010 16:04
> To: http://x-query.com/mailman/listinfo/talk
> Subject:  How is satisfies different from where ?
> 
> I've embarised to admit I've never used the sum/satisfies 
> expressions in XQuery.
> Im trying to grok this recently posted pastebin 
> http://pastebin.com/7GGQxpYH
> 
> quote----
> let $result1 := ( some $i in (1 to 5), $j in (5 to 10)
>    satisfies $j - $i = 0 )
> let $result2 := ( some $i in (1 to 5), $j in (6 to 10)
>    satisfies $j - $i = 0 )
> return
> <test>
> <result1>{$result1}</result1>
> <result2>{$result2}</result2>
> </test>
> 
> ----
> 
> How is this different from
> 
> --------
> <test>
> <result1>{ exists(
> for $i in (1 to 5) , $j in (5 to 10)
> where $j - $i = 0 return  $i
> )}</result1>
> <result2>{
> exists(
> for $i in (1 to 5) ,  $j in (6 to 20)
> where $j - $i = 0 return $i
> )}</result2>
> </test>
> 
> 
> 
> ---------------
> 
> More generaly what does satisfies/sum do differently then for/where ?
> Is it simply a shorter version of the same ? or is there a 
> operaitonal difference ?
> Where would I want to use some/satisfies where for/where is 
> either inappropreate or clumbsy ?
> 
> 
> 
> Thanks for any insight
> 
> 
> 
> 
> 
> 
> 
> --
> -------------------------
> David A. Lee
> http://x-query.com/mailman/listinfo/talk
> http://www.calldei.com
> http://www.xmlsh.org
> 
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