- From: Adam Retter <adam@exist-db.org>
- Date: Thu, 25 Aug 2016 12:50:32 +0100
- To: Hans-Juergen Rennau <hrennau@yahoo.de>
- Cc: Christian Grün <christian.gruen@gmail.com>, EXPath ML <public-expath@w3.org>
So... the way I would explain it for eXist is, that the util:eval
function example that I gave, executes code within the current XQuery
Context, so everything in the host XQuery is available to the
dynamically evaluated query. We also have a version of util:eval where
you can request a new context if you wanted isolation.
On 25 August 2016 at 12:26, Hans-Juergen Rennau <hrennau@yahoo.de> wrote:
> Thank you, Adam - interesting. So your example seems to show that you can
> leverage the binding of values to external variables (declared within the
> expression text) in order to give access to "external" functions, that is,
> functions defined in the context of the eval operation.
>
> Cheers,
> Hans-Jürgen
>
>
> Adam Retter <adam@exist-db.org> schrieb am 1:19 Donnerstag, 25.August 2016:
>
>
> Hans,
>
> You might already know this, but I thought I would mention... there is
> nothing that I know of in the spec that would prevent this, as it is
> up to the implementation about what the `eval` function does.
>
> You might also be interested to know that both eXist and MarkLogic
> support such a thing with their `eval` function implementations. For
> example in eXist:
>
> xquery version "3.0";
> declare function local:f() { 'hello' };
> let $ exprText: = 'declare variable $func external; $func()'
> return util:eval($exprText, false(), (xs:QName("func"), local:f#0))
>
>
> Cheers Adam.
>
> 2016-08-24 22:19 GMT+01:00 Hans-Juergen Rennau <hrennau@yahoo.de>:
>> Hi Christian,
>>
>> vermutlich bist Du in Urlaub; falls nicht - kannst Du mir einem Tip
>> weiterhelfen?
>>
>> Gibt es irgendeine Möglichkeit, in einem Ausdruck, der per xquery:eval
>> ausgewertet wird, eine Funktion aufzurufen, die in der Umgebeung definiert
>> wurde?
>>
>> Demo-Beispiel: das klappt nicht:
>> ------------------------------------------------------
>> declare function local:f() {'hello'};
>>
>> let $exprText := '$func()'
>> return xquery:eval($exprText, map{'func':local:f#0})
>> ------------------------------------------------------
>> =>
>> [XPST0008] Undefined variable $func.
>>
>> Was ich wollte, war, im als Text vorliegenden Ausdruck die Funktion
>> local:f() aufrufen, welche in der Umgebung von xquery:eval definiert ist.
>>
>> Das geht nicht, und vermutlich gibt es grundsätzlich keine Möglichkeit,
>> auf
>> Funktionen von "außen" zuzugreifen.
>>
>> Richtig?
>>
>> Viele Grüße,
>> Hans-Jürgen
>
>
>
>
> --
> Adam Retter
>
> eXist Developer
> { United Kingdom }
> adam@exist-db.org
> irc://irc.freenode.net/existdb
>
--
Adam Retter
eXist Developer
{ United Kingdom }
adam@exist-db.org
irc://irc.freenode.net/existdb
Received on Thursday, 25 August 2016 11:51:02 UTC