RE: [xml-dev] Dynamic function names

["Michael Kay" <mike@saxonica.com>]

Unfortunately XQuery has neither higher-order functions nor dynamic evaluation. (With higher-order functions, the variable doesn't hold the name of the function as a string, it holds a reference to the function as a first class object). However, many implementations do have an eval() function (in saxon it's called saxon:evaluate()) and some (including Saxon-SA) also have a capability for higher-order functions.

 

If you're prepared to consider XSLT rather than XQuery, Dimitre Novatchev's FXSL library provides a full implementation of higher-order programming in 100% portable XSLT code (this is possible in XSLT because it can ride on the dynamic despatch mechanism offered by xsl:apply-templates).

 

Michael Kay

http://www.saxonica.com/

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From: Ignacio Tripodi [mailto:ignaciot@gmail.com]
Sent: 08 August 2008 19:54
To: xml-dev@lists.xml.org
Subject: [xml-dev] Dynamic function names

Is this possible to do with XQuery? I'd like to be able to eval() a function whose name I'm getting from a variable. In a nutshell, I would have an attribute whose value is the function name that needs to be called. Something like:

                let $func_name := //blah[@function_to_run]
                let $func_argument := //blah[@some_id]
                let $result := eval($func_name( $att_value ))

which would basically execute the function whose name is $func_name, passing it $func_argument as the only argument and storing the result in $result. Of course, the 3rd line does not work and it's only to show what I'm trying to accomplish. Is there any way to accomplish this, not necessarily using eval()?

Any help will be greatly appreciated!

-i