RE: [xsl] xsl:function

["Michael Kay" <mhk@xxxxxxxxx>]

You can use any namespace you like for your functions, it's just there
to make sure that your functions don't conflict with anyone else's. If
you are writing a function library that will be widely deployed, use a
namesapce URI like http://namespaces.mega.co.jp/xslt/trig-module. If you
are writing something that will be used once and thrown away, and are
feeling lazy, use a namespace URI like "zzzz".

Note that a namespace URI is an identifier, not an address. It's a
unique name, it doesn't "point to" anything.

Michael Kay
Software AG
home: Michael.H.Kay@xxxxxxxxxxxx
work: Michael.Kay@xxxxxxxxxxxxxx 

> -----Original Message-----
> From: owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx 
> [mailto:owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Mac Martine
> Sent: 26 March 2003 22:56
> To: 'Jeni Tennison'
> Cc: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: RE: [xsl] xsl:function
> 
> 
> 
> Great, thanks. So, I think <func:function> will work, so I'm 
> trying to use that. I'm now just confused as to where the 
> namespace declaration should point. You use "my:", but I 
> don't know how I know where xmlns:my should point to. My 
> function is just going to return true or false after string 
> matching. According to everything I see on the web this is 
> considered common knowledge, so noone seems to explain 
> this... or I'm just overlooking something super simple. Anyway...
> Thanks-
>  Mac
> 
> 
> -----Original Message-----
> From: Jeni Tennison [mailto:jeni@xxxxxxxxxxxxxxxx] 
> Sent: Wednesday, March 26, 2003 1:58 PM
> To: Mac Martine
> Cc: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: Re: [xsl] xsl:function
> 
> Hi Mac,
> 
> > Would someone please give me a simple example of creating a user 
> > defined function using <xsl:function>
> >
> > I'm having a really hard time finding complete examples for some 
> > reason.
> 
> I suspect that's because <xsl:function> was only introduced 
> in XSLT 2.0, which isn't even a Last Call Working Draft yet 
> and has very few implementations.
> 
> <xsl:function> works in roughly the same way as 
> <func:function> as defined in EXSLT 
> (http://www.exslt.org/func/elements/function). You can find 
> lots of examples of <func:function> on the EXSLT site -- most 
> of the functions defined there have a <func:function> implementation.
> 
> An example is the following fairly useless function that adds 
> two things together:
> 
> <xsl:function name="my:add">
>   <xsl:param name="val1" />
>   <xsl:param name="val2" />
>   <xsl:result select="$val1 + $val2" />
> </xsl:function>
> 
> All functions you define with <xsl:function> have to be in 
> some namespace, which means that their names are always 
> qualified. In this example, you have to have the 'my' prefix 
> associated with a namespace at the top of your stylesheet.
> 
> You can call the function with, for example:
> 
>   <xsl:value-of select="my:add(1, 3)" />
> 
> to get the value 4.
>   
> If you want, you can constrain the types of the parameters to 
> the function and declare the type of the result using 'as' 
> attributes. This will enable/force the implementation to 
> raise type errors if the function is passed the wrong type of 
> arguments or used somewhere that expects something other than 
> a number. For example, to create a
> my:add() function that will only work with integers:
> 
> <xsl:function name="my:add">
>   <xsl:param name="val1" as="xs:integer" />
>   <xsl:param name="val2" as="xs:integer" />
>   <xsl:result select="$val1 + $val2" as="xs:integer" /> 
> </xsl:function>
> 
> Note again that the 'xs' prefix has to be associated with the 
> 'http://www.w3.org/2001/XMLSchema' namespace > at the top of 
> your stylesheet.
> 
> If you're after concrete examples of user-defined functions 
> in use, I used quite a few in some stylesheets I wrote over 
> the weekend, which are available at:
> 
  http://www.lmnl.org/projects/LMNLCreator/LMNLCreator.xsl
  http://www.lmnl.org/projects/LMNLSchema/LMNLNester.xsl

The stylesheets are not run-of-the-mill, but they do use XSLT 2.0
features, including <xsl:function>, quite heavily.

Cheers,

Jeni

---
Jeni Tennison
http://www.jenitennison.com/



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